Kidney Function Lab Results: eGFR, Creatinine, and Questions Before a New Medicine

By MedicalFoundationofNC.org Editorial Team

This article is educational and is not medical advice. It cannot tell you what your own result means or whether a medicine is right for you. Your clinician and pharmacist can. See our Medical Disclaimer.

The Short Answer: What eGFR and Creatinine Measure

Creatinine is a waste product your body makes when muscle tissue breaks down. Your kidneys normally filter it out of your blood and remove it in urine, so if the kidneys are not working well, creatinine can build up in the blood (MedlinePlus). The National Kidney Foundation (NKF) adds that creatinine also comes from digesting dietary protein (NKF).

eGFR (estimated glomerular filtration rate) is a calculated estimate of how well your kidneys are filtering your blood. It is usually worked out from a blood creatinine result. MedlinePlus says the calculation includes your age, weight, height, and sex (MedlinePlus).

Both tests are clues, not verdicts. A single number does not diagnose a kidney condition. If a new medicine is being considered, your kidney results may be one piece of what your clinician and pharmacist look at, and the card below helps you ask about it.

Why Doctors Use eGFR Instead of Creatinine Alone

MedlinePlus explains that creatinine alone is not the best way to check kidney function. People make different amounts of creatinine depending on muscle mass, diet, age, and activity level. A calculated eGFR is a more accurate way to judge kidney health than a blood or urine creatinine level by itself (MedlinePlus).

The NKF explains that directly measuring GFR is long and complex, so healthcare professionals usually use a formula to estimate it instead (NKF).

How eGFR Numbers Are Grouped

The NKF describes these general eGFR ranges for adults:

90 or higher: in the normal range
60 to 89: may mean early-stage kidney disease
15 to 59: may mean kidney disease
Below 15: may mean kidney failure

The NKF also notes that eGFR declines with age even in people without kidney disease. Its published averages by age are:

Ages 20 to 29: 116
Ages 30 to 39: 107
Ages 40 to 49: 99
Ages 50 to 59: 93
Ages 60 to 69: 85
Ages 70 and older: 75

Chronic kidney disease (CKD) is divided into five stages, with stage 3 split into 3a (eGFR 45 to 59) and 3b (30 to 44). Stage 4 is 15 to 29, and stage 5 is below 15. The NKF says your healthcare professional determines your stage. Its staging table also describes stages 1 and 2 alongside signs of kidney damage, such as protein in the urine, so a clinician usually looks at more than one number (NKF).

Why a Result Can Be Misleading

These limits matter most when a medicine decision is involved:

A normal creatinine does not always mean healthy kidneys. MedlinePlus says blood creatinine can stay in the normal range during early kidney disease and rise as the condition becomes more serious (MedlinePlus).
A high creatinine does not always mean a kidney problem. MedlinePlus lists dehydration, muscle disorders and injuries, intense exercise, and a diet high in meat as possible causes. A single high result cannot diagnose a specific condition, and you will likely need retesting or other tests (MedlinePlus).
eGFR is an estimate. The NKF says it can be inaccurate, especially in early kidney disease, and can miss early changes. Other factors that can affect it include pregnancy, being over 70, unusual muscle mass, cirrhosis, nephrotic syndrome, a past solid organ transplant, and some medications (NKF).
Other tests add context. MedlinePlus describes a urine albumin-to-creatinine ratio (UACR), which looks for albumin, a protein, in urine as a possible sign of kidney damage. The NKF’s suggested questions also include asking whether a urine albumin test makes sense for you.

If your clinician suspects a kidney problem, MedlinePlus notes that other kidney tests will likely follow even if your creatinine looks normal.

Why Kidney Results Can Matter for a Medicine Decision

Kidney testing and medicines connect in two ways, according to the sources:

MedlinePlus says creatinine testing is used to help check for side effects from medicines that may affect the kidneys.
The NKF’s suggested questions for your care team include whether any current medicines should be adjusted because of reduced kidney function, and whether any of your medicines could affect your kidneys. It also says some medicines can change test results.

Neither source gives medicine-specific dose rules. Whether a dose or drug changes for someone with a given kidney result is a decision for the prescriber and pharmacist, who know the medicine, the dose, and your full history.

Do not stop or change a medicine on your own because of a lab number. MedlinePlus advises not to stop taking any medicine unless your provider tells you to.

Lab-Question Card: Copy This Into Your Notes

Fill in what you can before your appointment or pharmacy visit. Blanks are fine, since “I don’t know” is a useful answer to bring.

1. Your Results

Test date: ________
Lab or clinic that ran the test: ________
eGFR: ________ (write the unit exactly as printed on your report)
Creatinine: ________ (write the unit exactly as printed)
Reference range printed on my report: ________
Other kidney tests done, such as a urine albumin test (UACR) or another blood marker: ________

2. The Trend

Earlier eGFR and creatinine results, with dates: ________
Ask: Is my result up, down, or steady compared with before? (The NKF notes that trends over time are often more helpful than one number.)
Ask: Could anything have affected this result, such as dehydration, illness, intense exercise, a diet high in meat, or a new medicine or supplement?
Ask: Should this test be repeated, and when?

3. The Medicine Question

Medicine or supplement being considered: ________
Who prescribed or suggested it: ________
Dose being discussed: ________
Ask: Does my kidney result change whether this medicine is a good fit for me?
Ask: Does the dose need to be adjusted for my kidney function?
Ask: Should my kidney tests be checked again after I start?
Ask: Could any medicine or supplement I already take affect my kidneys?

4. Who Should Explain It

The clinician who ordered the test: ________ (for what the result means for you)
My pharmacist: ________ (you can also ask a pharmacist to go over your full medicine list and any dose questions)
A kidney specialist (nephrologist), if my clinician refers me: ________

How to Prepare for the Conversation

The NKF suggests bringing:

A list of everything you take, including prescriptions, over-the-counter medicines, vitamins, and herbal supplements
Copies of past lab results
Any symptoms you have noticed, even small ones
A family member or friend who can listen and take notes
Your own health goals

MedlinePlus adds that your provider may give preparation instructions for the test itself. For example, you may be told not to eat meat for 24 hours beforehand, or to fast if creatinine is part of a broader metabolic panel. Follow the instructions you are given.

Who Should Talk to a Clinician

Early chronic kidney disease often has no symptoms, so testing may be recommended based on risk. The NKF lists diabetes, high blood pressure, overweight or obesity, age over 60, and a family history of kidney disease or kidney failure as risk factors. MedlinePlus also lists heart disease, smoking, and age over 50. Our guides on blood pressure basics and monitoring and type 2 diabetes prevention cover two of those areas.

Symptoms that can go with kidney problems include more or less frequent urination, itching, tiredness, muscle cramps, nausea and vomiting, and loss of appetite. The NKF also lists swelling in the arms, legs, or feet, and MedlinePlus lists swelling in the hands and feet or puffy eyelids. If you have symptoms, an abnormal result, or a new medicine and a kidney question, contact your clinician or pharmacist. For sudden or severe symptoms, seek urgent medical care.

What to Do Next

Find your most recent eGFR and creatinine results and any earlier ones.
Fill in the lab-question card above.
Bring it, along with your full medicine and supplement list, to your clinician or pharmacist.
Ask them to explain the numbers in the context of your history before any medicine change.

For another lab-reading guide, see our Cholesterol and Lipid Panel Interpretation Guide. To report an error in this article, use our Contact page. See also Our Standards & Disclosures.

Sources

National Kidney Foundation. Estimated Glomerular Filtration Rate (eGFR). Page shows last updated February 5, 2026. Accessed September 29, 2026.
MedlinePlus, National Library of Medicine. Creatinine Test. Page shows last updated December 5, 2023. Accessed September 29, 2026.

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