When you take creatine to build muscle or boost energy, your body turns most of it into creatinine-a waste product your kidneys filter out. That’s normal. But here’s the problem: creatine makes your blood creatinine levels rise, and doctors use that number to check if your kidneys are working right. If you’re on kidney disease medications like ACE inhibitors or NSAIDs, that spike can look like kidney damage… even when it’s not.
Why Creatine Messes With Kidney Tests
Creatine monohydrate is the most studied supplement in sports science. About 90% of what you take ends up as creatinine, which gets measured in every basic blood test. Labs use that number to calculate your eGFR-the gold standard for estimating kidney function. But creatine supplementation can push creatinine up by 10% to 30%. That’s not kidney damage. That’s chemistry.Take a healthy 30-year-old who takes 5 grams of creatine daily. Their creatinine might jump from 1.0 mg/dL to 1.2 or even 1.3. Their eGFR, which was 95, could drop to 78. That’s the threshold for stage 2 chronic kidney disease. But their kidneys? Still fine. Their urine output? Normal. Their blood urea nitrogen? Stable. Their cystatin C-a better marker unaffected by creatine? Unchanged. They’re not in kidney trouble. They’re just taking a supplement.
This isn’t theory. It’s documented. A 2000 study in the Journal of Strength and Conditioning Research followed 48 healthy people taking creatine for weeks. No drop in kidney function. Just higher creatinine. Same result in older adults, athletes, sedentary folks. Even a 2024 Mendelian randomization study-using genetic data to prove cause and effect-found zero link between creatine and actual kidney damage. The rise in creatinine? Pure artifact.
What Happens When You’re on Kidney Medications
Now imagine you’re on lisinopril, losartan, or another ACE inhibitor or ARB for high blood pressure or kidney protection. These drugs slow down kidney filtration slightly. That’s intentional. They’re meant to reduce protein loss and lower pressure in the tiny kidney filters.But add creatine on top? Now your creatinine is rising from two directions: the supplement and the medication. Your doctor sees a 20% increase in creatinine and thinks: Is the medication failing? Is the kidney getting worse? They might adjust your dose, order more tests, or even refer you to a nephrologist. All because of a supplement you didn’t even think was relevant.
Worse, some people with early kidney disease are told to take creatine for muscle loss or fatigue-without realizing it could mask real decline. If your kidneys are already struggling, adding creatine might make it harder to spot when things are getting worse. That’s why experts like the National Kidney Foundation say: if you have kidney disease, don’t start creatine without talking to your doctor.
What the Evidence Really Says
There are two kinds of stories here. The first: thousands of people taking creatine daily for years with clean kidneys. The second: a handful of case reports where someone got kidney damage while taking it.The case reports? They’re rare. One from 2011 described a man who developed acute tubular necrosis on 3 grams of creatine. No other risk factors. No other drugs. Just creatine. But that’s one person out of millions. The same report admitted this was an extreme outlier. Most studies-including reviews of over 500 people-show no harm. UCLA Health, the American College of Sports Medicine, and the European Food Safety Authority all agree: creatine is safe for healthy people.
But safety isn’t the same as simplicity. Just because it’s safe doesn’t mean it’s easy to monitor. The real danger isn’t creatine. It’s misinterpretation. A 2021 survey found 67% of primary care doctors didn’t know creatine could falsely raise creatinine. They saw a high number, assumed kidney trouble, and acted on it. One Reddit user got diagnosed with stage 2 CKD while taking 5 grams a day. After stopping creatine, their eGFR jumped back to normal. No treatment. No damage. Just a lab number that lied.
How to Monitor Your Kidneys Correctly
If you’re on kidney disease meds and want to take creatine-or if you’re already taking it-here’s what you need to do:- Get a baseline test before starting. Record your creatinine, eGFR, and blood urea nitrogen. Keep a copy.
- Ask for cystatin C. This is the key. Cystatin C isn’t affected by creatine. If your eGFR based on cystatin C stays normal while creatinine rises, your kidneys are fine. Many labs can run it. Ask your doctor.
- Use 24-hour urine creatinine clearance if cystatin C isn’t available. This measures how much creatinine your kidneys actually flush out in a day. If it’s stable, your filtration hasn’t changed.
- Don’t rely on eGFR alone. If your creatinine jumps and you’re on creatine, pause the supplement for 2 weeks and retest. If it drops back to baseline, it was creatine-not your kidneys.
- Tell every doctor you see. Add creatine to your medication list. Don’t assume they’ll ask. Most won’t.
There’s no magic formula yet, but research is moving fast. The University of Toronto presented data in 2023 suggesting a 0.9 multiplier for creatine users-meaning you could adjust your creatinine number down by 10% before calculating eGFR. That’s not official yet, but it’s coming.
What About ‘Kidney-Safe’ Creatine?
You’ll see products labeled “renal-friendly creatine,” “low-creatinine creatine,” or “clean creatine.” They sound smart. They’re not. All creatine monohydrate breaks down into creatinine. There’s no version that doesn’t. ConsumerLab.com tested these products in 2024 and found no difference in creatinine output. They’re marketing gimmicks. Save your money.
When to Avoid Creatine Altogether
You should not take creatine if:- You have diagnosed chronic kidney disease (eGFR under 60 for 3+ months)
- You’re on dialysis
- You’re taking multiple nephrotoxic drugs (like NSAIDs, certain antibiotics, or contrast dyes)
- You have uncontrolled high blood pressure
- Your doctor has warned you to avoid supplements that stress your kidneys
If you’re unsure, don’t guess. Get your kidney function checked first. Even if you’re healthy, baseline data gives you a reference point. It’s like keeping a log of your weight before starting a new workout plan.
The Bigger Picture
Creatine isn’t a drug. It’s a natural compound your body already makes. It’s safe. But it’s not invisible. It changes how your body looks on a kidney test. And that matters-especially if you’re managing a chronic condition.Doctors aren’t failing you. They’re working with outdated tools. The system wasn’t built for people who take supplements. But you can fix that. By knowing the science, asking the right questions, and pushing for better tests, you protect yourself from false alarms and unnecessary stress.
Don’t stop creatine because of fear. Stop it only if your doctor says your kidneys are truly declining. And if your creatinine goes up? Ask: Is this my kidneys… or just my supplement?
Can creatine cause kidney damage in healthy people?
No, current evidence shows creatine does not cause kidney damage in healthy individuals. Multiple studies, including long-term trials and a 2024 Mendelian randomization study, confirm that while creatine raises serum creatinine levels, it does not impair actual kidney function. The rise in creatinine is a metabolic side effect, not a sign of harm.
Why does my eGFR drop when I take creatine?
eGFR is calculated using your serum creatinine level. Creatine supplementation increases creatinine in your blood, which tricks the eGFR formula into thinking your kidneys are filtering less efficiently. This is a false reading. Your actual kidney function hasn’t changed. To get the real picture, ask for a cystatin C-based eGFR test, which isn’t affected by creatine.
Should I stop creatine if I have kidney disease?
Yes, if you have diagnosed chronic kidney disease (eGFR under 60), you should avoid creatine unless specifically approved by your nephrologist. While creatine doesn’t cause kidney damage, it can interfere with monitoring and make it harder to detect real decline. In advanced kidney disease, even small metabolic changes can stress your system.
Do kidney medications like ACE inhibitors interact with creatine?
They don’t directly interact in a toxic way, but they can make creatinine levels harder to interpret. ACE inhibitors lower kidney filtration slightly, and creatine raises creatinine. Together, they can create a misleading picture that looks like worsening kidney function. Always inform your doctor if you’re taking both. Use cystatin C or 24-hour urine clearance to get accurate readings.
What’s the best way to check kidney function if I take creatine?
The most accurate method is a cystatin C-based eGFR test (CKD-EPI CysC). It’s not affected by muscle mass or creatine use. If cystatin C isn’t available, a 24-hour urine creatinine clearance test gives a direct measure of filtration rate. Avoid relying on serum creatinine alone. Always compare results before and after starting creatine to spot true changes.
Are ‘kidney-safe’ creatine supplements real?
No. All creatine monohydrate breaks down into creatinine, regardless of branding. Products labeled as “kidney-safe” or “low-creatinine” are marketing claims with no scientific backing. ConsumerLab.com tested these in 2024 and found no difference in creatinine output compared to standard creatine. Stick with plain creatine monohydrate and monitor your kidney function properly instead.
What to Do Next
If you’re on kidney medications and taking creatine: schedule a cystatin C test. Bring your supplement list. Ask your doctor to compare your results before and after starting creatine. If you’re not taking it yet but want to: get your baseline numbers first. Don’t wait until your eGFR drops and you’re blindsided.Knowledge is your best tool. Creatine isn’t the enemy. Misunderstanding is. With the right tests and clear communication, you can keep taking it safely-even with kidney disease meds.