How Kidney Function Tests Guide Renal Pharmacotherapy and Why They Are Repeated

The appointment was supposed to be about blood pressure. Then the clinician slid a lab requisition across the desk: creatinine, eGFR, a urine sample. “I thought we were talking about my heart,” the man in his sixties said, half joking. Anyone who has been asked for kidney function tests before medication has probably felt that same small flicker of confusion, followed by a quieter worry: does she think something is wrong with my kidneys?

Usually, no. What the prescriber is doing is closer to checking a river’s flow before deciding how much to pour in. Many medicines leave the body through the kidneys, and the speed of that exit shapes how much of a drug lingers in the blood. Two people can swallow identical prescriptions and end up with very different levels circulating a week later, simply because their kidneys filter at different rates.

That is why the slip appears before the first prescription, and why it tends to reappear months later. This article explains what those tests measure, how the numbers steer treatment decisions, and why repetition is not fussiness but the whole point.

What are kidney function tests before medication, and what do they actually check?

A kidney function test is a small set of blood and urine measurements that estimate how efficiently the kidneys filter waste from the blood. The most common trio is serum creatinine, the estimated glomerular filtration rate, and a urine albumin-to-creatinine ratio. Each answers a slightly different question.

Creatinine is a waste product made steadily by muscles as they use energy. Healthy kidneys remove it at a fairly constant rate, so when creatinine builds up in the blood, filtration has usually slowed. On its own, though, the number is hard to read: a muscular thirty-year-old and a frail eighty-year-old can both sit at the same creatinine value while their kidneys are doing very different work.

The estimated glomerular filtration rate, or eGFR, solves part of that problem. A glomerulus is one of roughly a million tiny filtering units in each kidney; the eGFR is a calculation that uses creatinine along with age and sex to estimate how many milliliters of blood those filters clean each minute. According to the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases, an eGFR of 60 or higher is generally considered within the normal range, while a value below 60 that persists for three months or more is one definition of chronic kidney disease.

The urine test looks for albumin, the main protein in blood. Healthy filters keep albumin in the bloodstream; leaky ones let it escape into urine. Albumin in urine can flag kidney damage long before eGFR drops, which is why it sits alongside the blood tests rather than replacing them.

When a prescriber orders these before a new medicine, they are establishing a baseline: a snapshot of how your kidneys work today, against which every future result will be compared.

How do the kidneys clear a medicine, in plain language?

Picture the kidneys as a pair of fist-sized filtration plants receiving about half a cup of blood every minute, a figure the NIDDK uses to describe normal filtering. Blood arrives under pressure, passes through the glomeruli, and a filtrate of water, salts, and small molecules drips into a network of tubules. Most of the water and useful substances are pulled back into the blood. What remains becomes urine.

Many medicines are small enough to pass through that sieve. Some are also actively pumped into the tubules by transporter proteins. Either way, the drug leaves the body at a rate that depends on how much blood the filters handle. A person whose eGFR is half the expected value clears a kidney-dependent drug roughly half as fast, which means the same repeated dose produces a blood level close to double what the prescriber intended.

Not every medicine works this way. Some are broken down mainly by the liver and barely touch the kidneys. Others are partly cleared by both organs. The prescriber’s mental checklist runs something like this: Is this drug removed by the kidneys? Does it have a narrow margin between a helpful level and a harmful one? Does it have the potential to injure the kidney itself? A yes to any of those makes a baseline kidney test more valuable.

There is a second, less obvious reason. Some medicines change how the kidney behaves without damaging it. Drugs that relax blood vessels leading out of the glomerulus, or that alter salt handling, can shift the eGFR reading within days of the first dose. Knowing the starting point is the only way to tell an expected, benign shift from a genuine problem.

Is there a single golden test for kidney function?

People often ask for the one definitive test. The honest answer is that the true gold standard, measured GFR, is rarely used in everyday care. It involves injecting a marker substance that the kidneys filter but do not reabsorb or secrete, then timing how quickly it disappears from the blood. It is accurate, slow, and impractical for routine prescribing decisions.

So clinicians rely on estimates. The eGFR calculated from creatinine is the workhorse because it is cheap, widely available, and good enough for most decisions. The equation now recommended in the United States no longer includes a race variable, a change the NIDDK describes as part of an effort to make estimates fairer across populations.

When creatinine is likely to mislead, there is a second option. Cystatin C is a small protein produced by nearly all cells at a steady rate, largely independent of muscle mass. An eGFR based on cystatin C, or on both markers together, can be a useful confirmatory test in people with very high or very low muscle mass, in those with liver disease, or when a creatinine-based result sits close to a treatment threshold. The NIDDK notes it is used when a more accurate estimate is needed.

The urine albumin-to-creatinine ratio is not a filtration test at all, yet it belongs in any conversation about a “golden” test. It detects damage to the filter’s structure rather than a slowdown in its speed. Guideline bodies increasingly treat eGFR and albuminuria as a pair, because someone can have a normal eGFR and still be leaking protein, and that combination changes risk considerably.

The practical takeaway: there is no single perfect number. There is a well-understood set of imperfect ones, read together.

eGFR blood test meaning, creatinine, urine albumin and cystatin C compared

The table below summarizes what each test measures and what tends to move it. Reference ranges vary a little between laboratories, so the printed range on your own report is the one that matters.

Test	Sample	What it estimates	Common non-kidney influences
Serum creatinine	Blood	Waste level that rises as filtration slows	Muscle mass, recent cooked-meat meal, creatine supplements, some antibiotics and acid-reducers
eGFR (creatinine-based)	Calculated	Filtration rate in mL/min/1.73 m²	Everything that affects creatinine, plus age and sex entered into the formula
Cystatin C	Blood	Filtration rate less dependent on muscle	Thyroid disease, steroid use, obesity, inflammation
Urine albumin-to-creatinine ratio	Urine	Protein leak from damaged filters	Fever, urinary infection, heavy exercise, menstruation, uncontrolled blood sugar
Blood urea nitrogen (BUN)	Blood	Second waste marker	Dehydration, high-protein diet, bleeding in the gut, liver disease

A few reading tips help. An eGFR of 90 or above is generally reported as normal; 60 to 89 is often described as mildly reduced and may be perfectly healthy for an older adult; below 60 warrants attention, and below 15 is the range Mayo Clinic describes as kidney failure. Those cutoffs describe categories, not destinies.

BUN rarely drives prescribing on its own. It rises with dehydration and protein intake more readily than creatinine does, so a high BUN alongside a normal creatinine often points toward fluid status rather than kidney disease. Electrolytes such as potassium and sodium usually travel on the same panel, because several medicine classes that affect the kidney also shift potassium.

Why are kidney function tests before medication repeated after you start treatment?

A baseline is a photograph. Kidney function is a film. Repeating the test turns one frame into a sequence, and it is the sequence that tells the story.

The first reason for repetition is that some medicines nudge the eGFR in the days after starting. Drugs that block the renin-angiotensin system, the hormone pathway that tightens the small vessels leaving the glomerulus, typically cause a modest, expected dip in eGFR as filtration pressure eases. Newer glucose-lowering medicines that act on the kidney’s sodium-glucose transporters do something similar. A small fall in this context is usually a sign the drug is doing what it was designed to do, and it often stabilizes. A large fall is a different matter. Without a repeat test, no one can tell which is happening.

The second reason is that kidneys respond to life, not just to prescriptions. A stomach bug, a hot week with too little fluid, a course of anti-inflammatory painkillers, or a hospital scan with iodinated contrast can all temporarily reduce filtration. A medicine that was safely cleared last month may accumulate this month.

The third reason is that creatinine is a slow messenger. After an injury to the kidney, creatinine takes time to rise because it must accumulate in the blood before the number moves. A test drawn too early can look reassuring while filtration is already falling. Clinicians sometimes describe the pattern using the term acute kidney injury, which simply means a sudden drop in kidney function over hours to days, often reversible when the cause is removed.

The NHS advises that people diagnosed with chronic kidney disease have regular tests, at least yearly, to track whether function is stable or drifting. For people on kidney-sensitive medicines, the prescriber sets the interval, usually closer together after any change and further apart once results settle.

Which medicine classes most often require kidney checks?

Mentioning classes here is descriptive, not a recommendation. Whether any of these applies to you is entirely a question for the person prescribing.

• Blood pressure medicines acting on the renin-angiotensin system (ACE inhibitors and angiotensin receptor blockers). These protect the kidney over the long term in many conditions but can lower eGFR and raise potassium early on, so checks before and shortly after starting are routine.
• Diuretics, which increase urine output. They can concentrate the blood and shift electrolytes, especially if fluid intake falls during illness.
• Non-steroidal anti-inflammatory drugs, including several sold without prescription. They reduce blood flow into the glomerulus, and the effect is amplified in people who are dehydrated or already taking the first two classes above.
• Certain glucose-lowering medicines, including biguanides and SGLT2 inhibitors, whose use and monitoring depend on the eGFR range.
• Some anticoagulants, whose blood levels rise as clearance falls, increasing bleeding risk.
• Specific antibiotics and antivirals cleared largely by the kidney, where levels must be kept within a narrow window.
• Mood stabilizers such as lithium, which has a narrow safety margin and can itself affect the kidney over years.
• Iodinated contrast for CT scans, where an eGFR is commonly checked beforehand, particularly in people with existing kidney disease or diabetes.

Cleveland Clinic and Mayo Clinic both describe kidney function testing as part of monitoring for medicines that can affect the kidneys or that rely on the kidneys for clearance. The common thread is not that these drugs are dangerous; it is that their behavior depends on a number that can change. A prescriber who knows that number can often keep a valuable medicine in use safely by adjusting how it is given, something no one should attempt on their own.

Who is usually tested first, and who is asked to wait?

Not everyone starting a prescription gets a kidney panel. The people most often tested share features that raise either the chance of reduced filtration or the stakes of missing it.

Diabetes and high blood pressure top the list; the CDC identifies them as the leading causes of chronic kidney disease in the United States. Heart failure, a family history of kidney disease, prior acute kidney injury, and older age also prompt testing, as does any planned medicine from the classes described above. The NIDDK recommends that people with diabetes or high blood pressure be tested for kidney disease regularly, because early disease produces no symptoms, and the CDC notes that most people with CKD are unaware they have it.

Being asked to wait is common, and it is usually about timing rather than concern. A person who has just recovered from a vomiting illness may be told to come back in a week or two, because a test drawn while dehydrated will understate true kidney function and could lead to an unnecessarily cautious decision. Someone who had a CT scan with contrast a few days earlier may be asked to delay so the scan’s transient effect does not muddy the baseline. A urinary tract infection or a fever can push albumin into the urine temporarily, so a positive albumin result during illness is generally repeated once the person is well.

Pregnancy is a special case. Filtration rises during pregnancy, so creatinine falls, and standard eGFR equations were not designed for pregnant people. Obstetric teams interpret these tests differently and may use other markers.

Waiting, in short, protects the quality of the information. A slightly delayed accurate result is more useful than a prompt misleading one, and the decision about when to draw blood rests with the clinician who will act on it.

What can affect kidney function test results and throw them off?

Creatinine is a muscle by-product, so anything that changes muscle turnover moves the number without the kidneys doing anything different. A large serving of cooked meat can raise creatinine for several hours, because cooking converts muscle creatine into creatinine that the gut absorbs. Creatine supplements popular among gym-goers do the same more persistently. Very muscular people run high; people with muscle loss from age, illness, or limb amputation run low, which can make an eGFR look better than the kidneys deserve.

Hydration pulls in both directions. Dehydration concentrates the blood and reduces filtration, nudging creatinine and BUN upward. Over-hydrating before a test does not meaningfully improve kidney numbers; it just dilutes the urine sample.

Strenuous exercise in the day before testing can raise creatinine and, more noticeably, spill albumin into the urine. So can fever, a urinary infection, menstrual blood in the sample, and poorly controlled blood sugar. MedlinePlus notes that a urine albumin result should be confirmed on repeat testing, partly for these reasons.

Several medicines interfere with the test rather than the kidney. Some antibiotics and stomach-acid reducers block the tubular pumps that secrete creatinine, raising the blood level while filtration is unchanged. A lipid-lowering fibrate can do the same. A clinician who knows the full medicine list can read around these effects, which is one reason the intake form asks about every tablet, supplement, and protein powder.

Finally, laboratory variation exists. The same sample run twice can differ slightly, and different labs calibrate a little differently. This is why prescribing decisions rarely hinge on a single value sitting a hair below a threshold, and why the repeat test carries so much weight. Trend beats snapshot.

What not to do before a kidney function test

Preparation is mostly about avoiding the things that distort results, and it is simpler than most people expect. Follow the instructions your own laboratory gives; where none are given, the points below reflect general guidance from MedlinePlus and Cleveland Clinic on creatinine and eGFR testing.

Avoid heavy or unusually intense exercise in the day before the draw. A long run or a hard weights session can raise creatinine and push protein into urine, making a healthy kidney look mildly stressed.

Skip the steak dinner the night before, or at least keep meat portions ordinary. Cooked meat raises creatinine for several hours afterward. Some laboratories ask for fasting because other tests share the same tube; if they ask, fast as instructed, but fasting is not required for creatinine itself.

Drink water as you normally would. Arriving parched will inflate the numbers; arriving after a liter of water will not deflate them, but it may make the urine sample too dilute to interpret.

Do not stop or skip a prescribed medicine to “clean up” the result. If a medicine affects the reading, the clinician needs to see the reading with the medicine on board, because that is the state in which you actually live. Any change to prescribed treatment is a decision for the prescriber, never a pre-test tactic.

Mention supplements, especially creatine and high-dose protein products, and any recent illness, fever, or urinary symptoms. For the urine sample, collect a midstream specimen unless told otherwise, and let the team know if you are menstruating; they may prefer to reschedule the urine portion.

None of this is about passing or failing. The goal is to hand the clinician a clear, undistorted picture of how the kidneys behave on an ordinary day.

What is the biggest indicator of kidney disease?

If forced to pick one, most kidney specialists would not choose eGFR. They would choose albumin in the urine. Persistent albuminuria, the medical term for protein leaking through damaged filters, tends to appear earlier than a fall in filtration, and it predicts both progression of kidney disease and cardiovascular events more strongly than eGFR alone across a wide range of studies summarized in guideline literature.

The reason is mechanical. The glomerular filter is a layered membrane designed to hold back proteins while letting water and small waste through. When high pressure or high blood sugar damages that membrane, albumin slips out long before enough filters fail to change the overall flow rate. A person with diabetes might show rising albumin years before eGFR drifts below 60. The NIDDK describes the urine albumin test as a key way to detect kidney damage early, and CDC materials frame the two tests, eGFR and urine albumin, as the standard screening pair.

That said, “biggest indicator” depends on the question. For deciding whether a medicine will accumulate, eGFR is the relevant number, because it measures clearance, not leakiness. For predicting whether kidney disease will worsen, albuminuria carries more weight. For diagnosis, both matter, and the NHS and Mayo Clinic describe combining them with imaging and, occasionally, a kidney biopsy when the cause is unclear.

Symptoms are a poor indicator. Swelling, fatigue, and changes in urination usually arrive late, when a substantial share of filtering capacity is already lost. This is the quiet argument for testing people at risk before anything feels wrong, and for treating a positive albumin result as information worth confirming rather than a verdict.

What the following days and weeks usually look like after a kidney test flags something

Most kidney function tests before medication come back unremarkable, and the prescription proceeds. When a result is unexpected, the pathway is usually measured rather than dramatic.

The first step is almost always a repeat. A single low eGFR or a single positive albumin result is not enough to diagnose chronic kidney disease; the definition requires abnormalities persisting for more than three months, according to the NIDDK, Mayo Clinic, and NHS alike. A clinician may order the repeat within a few weeks to rule out a temporary cause, then again after the three-month mark if the first repeat is still abnormal. During that window, the planned medicine may start at a more cautious level, be swapped for one less dependent on the kidney, or be delayed, depending on how urgent the underlying condition is.

If a medicine has already begun and the repeat shows the expected small dip, the typical response is reassurance and a further check at a longer interval. If the dip is larger than expected, the prescriber may pause, investigate other causes such as dehydration or an interacting drug, and recheck. These are judgment calls made with the whole picture in view.

A persistently abnormal pair of results usually leads to a fuller workup: blood pressure review, blood sugar testing, a kidney ultrasound to look at size and structure, and a conversation about risk factors. Referral to a nephrologist, a kidney specialist, becomes more likely as eGFR falls, as albumin rises, or when the cause is unclear.

For someone with stable, established kidney disease, the rhythm settles into annual or more frequent monitoring, as the NHS describes, with additional checks around any new prescription. The tests become less an event and more a habit, like a dental visit.

What people often get wrong about kidney tests and medicines

“A low eGFR means my kidneys are failing.” Kidney failure is generally described by Mayo Clinic as an eGFR below 15. An eGFR of 55 in a seventy-five-year-old may reflect ordinary aging; it still shapes prescribing, but it is not a crisis.

“The blood pressure pill damaged my kidneys because my eGFR dropped.” A modest early decline after starting a renin-angiotensin blocker is an expected effect of lowering pressure inside the filters, and these medicines are used precisely because they slow kidney damage over years in many conditions. Whether a particular fall is acceptable is a question only the prescriber can answer with the numbers in hand.

“I should drink lots of water before the test to get a better result.” Normal hydration is enough. Extra water does not improve filtration; it only dilutes urine.

“Over-the-counter painkillers are safe because they don’t need a prescription.” Non-steroidal anti-inflammatories are among the more common contributors to sudden kidney injury, especially in people who are dehydrated or taking diuretics or renin-angiotensin blockers. Availability without prescription says nothing about kidney safety.

“If the first test was fine, I don’t need the follow-up.” The follow-up exists because kidneys change. Skipping it removes the one tool that catches a problem while it is still small.

“Kidney disease would make me feel unwell.” The CDC notes that most people with chronic kidney disease do not know they have it, largely because early stages produce no symptoms.

“Protein in urine always means kidney disease.” Fever, exercise, infection, and menstruation can all produce a transient positive. That is why MedlinePlus and guideline bodies call for confirmation on repeat before drawing conclusions.

Correcting these ideas matters because they drive behavior: people stop helpful medicines, avoid needed tests, or take unhelpful ones.

Questions to ask your care team about kidney testing and your prescriptions

Good questions turn a lab slip into a conversation. Consider bringing a few of these, and writing down the answers.

• Which of my medicines are cleared mainly by the kidneys, and which could affect kidney function?
• What was my eGFR and my urine albumin result this time, and how do they compare with my last ones?
• Is this result being interpreted as my baseline, or as a change from an earlier baseline?
• If my eGFR shifts after I start this medicine, what size of change would you consider expected, and what would prompt a rethink?
• How often do you plan to repeat these tests, and what would make you want to check sooner?
• Are there over-the-counter medicines or supplements I should ask you about before taking them?
• If I get a vomiting or diarrheal illness, or cannot keep fluids down, is there anything about my medicines I should call you about? (Some teams give specific guidance for sick days; do not act on this without their instruction.)
• Should I avoid anything in the day before my next test, such as heavy exercise or a large meat meal?
• Would a cystatin C test add anything useful in my situation?
• Do my results suggest I should see a kidney specialist, and if not, what would change that?
• Does my blood pressure or blood sugar control affect these numbers, and what targets are we working toward?

Notice that none of these ask the clinician to promise an outcome. They ask for the reasoning, the thresholds, and the plan. A prescriber who explains why a repeat test is scheduled, and what would happen with a high or low result, is handing you the same map they are using. That shared map is what makes long-term monitoring feel like partnership rather than surveillance.

When to call your doctor: red-flag signs that should not wait for the next scheduled test

Routine kidney monitoring is designed to catch slow change. Some situations call for a same-day phone call or urgent care rather than waiting for the next appointment.

Contact your care team promptly, or seek urgent care, if you notice any of the following, particularly after starting or changing a medicine known to affect the kidneys:

• Passing much less urine than usual, or none, for a stretch of hours despite drinking normally.
• Sudden swelling of the legs, ankles, feet, or around the eyes, or rapid unexplained weight gain over a few days.
• New shortness of breath, especially when lying flat.
• Persistent vomiting or diarrhea that prevents you from keeping fluids down, particularly if you take diuretics, blood pressure medicines, or diabetes medicines.
• Marked confusion, unusual drowsiness, or new muscle weakness or an irregular heartbeat, which can accompany dangerous potassium levels.
• Blood in the urine, or urine that has turned dark brown or cola-colored.
• Severe pain in the side or back with fever, which may indicate a kidney infection or obstruction.
• A laboratory result flagged as critical or a call from the lab asking you to contact your clinician.

These signs do not confirm a kidney problem; several have other explanations. What they share is urgency: each can represent a sudden fall in kidney function or a dangerous electrolyte shift, both of which are more treatable when caught early. Mayo Clinic and the NHS describe acute kidney injury as often reversible when the cause is identified and addressed quickly.

Do not stop a prescribed medicine on your own while waiting for advice unless your team has already told you to do so in that situation. Call, describe what is happening, and let the people who know your baseline decide the next step. That is what the baseline was for.

Frequently asked questions

What can throw off a kidney function test?

Anything that changes creatinine production or clearance without changing the kidneys can distort the result. Large cooked-meat meals, creatine supplements, intense exercise, dehydration, and high or very low muscle mass all shift creatinine. Some antibiotics and acid-reducers block creatinine secretion in the tubules. For the urine albumin test, fever, infection, heavy exercise, and menstruation can cause temporary positives, which is why abnormal results are confirmed on repeat.

What is the golden test for kidney function?

The reference standard is measured GFR using an injected marker, but it is slow and rarely used outside research or complex cases. In everyday care, the creatinine-based eGFR paired with a urine albumin-to-creatinine ratio is the practical standard, with cystatin C as a confirmatory option when creatinine may mislead. No single number tells the whole story; clinicians read filtration and protein leak together.

What not to do before a kidney function test?

Avoid strenuous exercise and unusually large meat meals in the day beforehand, since both raise creatinine. Do not deliberately over-drink or under-drink; normal hydration is what the test should capture. Never stop or skip a prescribed medicine to improve the result, because the clinician needs to see your kidneys as they function on treatment. Mention supplements and recent illness, and follow any fasting instructions your laboratory gives.

What is the biggest indicator of kidney disease?

Persistent albumin in the urine is generally considered the earliest and most predictive marker of kidney damage, because filters leak protein before overall filtration slows. Estimated GFR is the key measure of how well the kidneys clear waste and medicines. Guideline bodies treat the two as a pair: eGFR describes how fast the kidney filters, albuminuria describes how damaged the filter is.

What are normal kidney function test results?

An eGFR of 90 or above is usually reported as normal, 60 to 89 as mildly reduced, and below 60 as reduced, with below 15 described as kidney failure. Urine albumin is typically reported as normal, moderately increased, or severely increased. Creatinine reference ranges differ by laboratory, age, sex, and muscle mass, so the range printed on your own report is the one your clinician will use.

Why did my eGFR drop after starting a blood pressure medicine?

Medicines that block the renin-angiotensin system relax the small vessels leaving the kidney’s filters, lowering pressure inside them. Filtration slows slightly as a result, so a modest early fall in eGFR is expected and often stabilizes. Whether a particular change is within the acceptable range is a judgment for the prescriber, who will compare it with your baseline and usually recheck before deciding anything.

How often are kidney function tests repeated on long-term medicines?

There is no single schedule. The NHS advises that people with chronic kidney disease are tested at least yearly, and many prescribers check more often soon after starting or changing a kidney-sensitive medicine, then space checks out once results are stable. Illness, dehydration, a contrast scan, or a new interacting medicine can prompt an earlier test. Your prescriber sets the interval based on your results and risk.

Does a low eGFR mean I cannot take a particular medicine?

Not necessarily. For many medicines cleared by the kidneys, a lower eGFR means the prescriber adjusts how the drug is given or monitors more closely, rather than avoiding it. For a smaller group with narrow safety margins, a low eGFR may lead to choosing an alternative. The decision depends on the specific drug, your eGFR range, other medicines, and the condition being treated, and rests with the prescribing clinician.

Can over-the-counter painkillers affect my kidney test results?

Yes. Non-steroidal anti-inflammatory drugs reduce blood flow into the kidney’s filters and can lower eGFR, especially in people who are dehydrated or taking diuretics or blood pressure medicines that act on the kidney. Occasional use in healthy people is usually uneventful, but anyone with reduced kidney function or on kidney-sensitive prescriptions should ask their care team before using them regularly.

Why do I need a urine test if my blood test was normal?

Because the two tests measure different things. Blood tests estimate how quickly the kidneys filter; the urine test detects protein leaking through damaged filters. Damage often shows up as albumin in urine while eGFR is still normal, particularly in diabetes and high blood pressure. Checking both gives an earlier and more complete picture, and a positive urine result is usually repeated to rule out temporary causes.

References

• Chronic kidney disease – Diagnosis (NHS)
• Chronic Kidney Disease Tests & Diagnosis (NIH – NIDDK)
• Kidney Function Tests (Cleveland Clinic)
• Glomerular Filtration Rate (GFR) Test (MedlinePlus)

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.