Does creatine supplementation damage your kidneys?

No. Creatine raises serum creatinine, a waste product used as a kidney marker, but this does not indicate kidney damage. The International Society of Sports Nutrition confirms creatine is safe for healthy kidneys at 3-5g per day, even long-term.

Should I stop creatine before a blood test?

It depends on what your doctor is testing. If kidney function (eGFR via creatinine) is being assessed, stopping creatine 3-5 days before can prevent a falsely low eGFR reading. Alternatively, ask your doctor for a Cystatin C-based eGFR test, which is not affected by creatine.

What is the difference between creatine and creatinine?

Creatine is a beneficial compound stored in muscles that helps regenerate ATP for energy. Creatinine is a metabolic waste product formed when creatine and phosphocreatine break down. Creatinine is filtered by the kidneys and excreted in urine, which is why it is used as a kidney health marker.

What is Cystatin C and why is it better for creatine users?

Cystatin C is a small protein produced by all nucleated cells at a constant rate. Unlike creatinine, its blood levels are not affected by muscle mass, diet, or creatine supplementation. A Cystatin C-based eGFR gives a more accurate kidney function reading for people who take creatine.

Creatine vs Creatinine: Why Your Blood Test Might Be Misleading

TL;DR — Creatine vs Creatinine

If you take creatine and your blood test shows elevated creatinine or a lower-than-expected eGFR, do not panic. Creatine supplementation naturally increases serum creatinine because creatinine is a normal breakdown product of creatine in your muscles. This is a measurement artifact, not a sign of kidney damage (RB et al., 2017) .

The simplest solution is to ask your doctor for a Cystatin C-based eGFR test, which is unaffected by creatine intake and gives an accurate picture of your kidney health.

20-30%

increase in serum creatinine commonly seen with creatine supplementation

Kreider et al., 2017 — ISSN Position Stand

What Is Creatine?

Creatine is a naturally occurring compound made from three amino acids: arginine, glycine, and methionine. Your body produces about 1-2g daily in the liver, kidneys, and pancreas. Additional creatine comes from dietary sources such as red meat and fish.

Once synthesized or consumed, creatine is transported to tissues with high energy demands — primarily skeletal muscle (which stores about 95% of total creatine) and the brain. Inside these cells, creatine is phosphorylated into phosphocreatine (PCr), which serves as a rapid energy buffer for regenerating ATP during high-intensity activity.

Supplementing with creatine monohydrate at 3-5g per day increases intramuscular creatine stores by roughly 20%, improving performance in short-duration, high-intensity tasks.

What Is Creatinine?

Creatinine is a waste product — the metabolic end-product of creatine and phosphocreatine breakdown. Every day, approximately 1.7% of your total creatine pool is irreversibly converted into creatinine through a non-enzymatic process called dehydration.

Creatinine is released into the bloodstream, filtered by the kidneys, and excreted in urine at a relatively constant rate. Because this excretion rate is stable, doctors use serum creatinine levels to estimate how well your kidneys are filtering blood. This estimate is called the estimated glomerular filtration rate (eGFR).

Why Creatine Supplementation Raises Creatinine

The relationship is straightforward:

More creatine in your muscles means a larger total creatine pool.
A larger creatine pool means more creatinine is produced as a natural byproduct of daily creatine turnover.
More creatinine production leads to higher serum creatinine levels on your blood test.

This is basic biochemistry, not pathology. The kidneys are still filtering at the same rate — there is simply more creatinine to filter. Studies have repeatedly confirmed that creatine supplementation does not impair renal function in healthy individuals (RB et al., 2017) .

1.7%

of total body creatine converts to creatinine daily through non-enzymatic breakdown

ISSN Position Stand on Creatine, 2017

The eGFR Problem for Creatine Users

The eGFR formula uses serum creatinine as its primary input variable. When creatine supplementation raises your creatinine, the formula interprets this as reduced kidney filtration — even though your kidneys are working perfectly.

Here is what typically happens:

Normal creatinine range: 0.7-1.3 mg/dL for men, 0.6-1.1 mg/dL for women.
On creatine: Levels may rise to 1.4-1.8 mg/dL or higher.
eGFR impact: A creatinine of 1.0 mg/dL might give an eGFR of 100 (normal). A creatinine of 1.5 mg/dL could drop the eGFR to 55-65, which looks like Stage 3 chronic kidney disease on paper — even though no disease exists.

This false reading can cause unnecessary alarm, additional testing, specialist referrals, and even pressure to stop supplementation when no clinical problem is present.

The Solution: Cystatin C Testing

Cystatin C is an alternative biomarker for estimating kidney function. It is a small protein produced at a constant rate by all nucleated cells in the body. Unlike creatinine, Cystatin C levels are:

Not affected by muscle mass — bodybuilders and sedentary individuals produce similar amounts.
Not affected by diet — eating more meat or taking creatine does not change Cystatin C.
Not affected by supplementation — creatine monohydrate has no impact on Cystatin C levels.

A Cystatin C-based eGFR (or a combined creatinine-Cystatin C eGFR) provides a far more accurate assessment of kidney function for creatine users, athletes, and anyone with above-average muscle mass.

Most hospital laboratories in Malaysia can run Cystatin C tests, though it may need to be specifically requested. The test typically costs RM50-150 depending on the facility.

How to Talk to Your Doctor About Creatine and Blood Tests

Many doctors are not aware that creatine supplementation affects creatinine readings. Here is a practical approach:

Before the blood test: Tell your doctor you are taking creatine monohydrate. Explain that it will likely raise your creatinine reading without indicating kidney problems.
Request Cystatin C: Ask for a Cystatin C-based eGFR if kidney function assessment is needed. This removes the creatine interference entirely.
Provide the research: Reference the ISSN Position Stand on creatine (Kreider et al., 2017), which explicitly addresses this issue and confirms creatine safety for healthy kidneys.
Consider a washout: If Cystatin C testing is unavailable, stopping creatine for 4-5 days before the blood draw can normalize creatinine levels for a more accurate traditional eGFR reading.

Who Should Be Extra Cautious?

While creatine is safe for healthy kidneys, certain individuals should consult their doctor before starting supplementation:

People with pre-existing kidney disease (CKD stage 3 or higher).
Those taking nephrotoxic medications such as certain NSAIDs, aminoglycoside antibiotics, or specific chemotherapy drugs.
Individuals with a single functioning kidney (though limited evidence suggests creatine may still be safe — medical supervision is recommended).

For these groups, baseline Cystatin C testing before starting creatine and periodic monitoring during supplementation is a prudent approach.

Key Takeaways

Creatine is a beneficial energy compound; creatinine is its harmless waste product.
Creatine supplementation raises serum creatinine and can cause a falsely low eGFR reading.
This does not indicate kidney damage — it is a measurement limitation.
Cystatin C-based eGFR is the gold standard for creatine users who need kidney function testing.
Always inform your doctor that you take creatine before any blood work.
The ISSN confirms creatine monohydrate is safe for healthy kidneys at standard doses (RB et al., 2017) .