Several common supplements can raise your serum creatinine levels, and most of the time the increase doesn’t reflect actual kidney damage. Creatine monohydrate is the most well-known culprit, but high-protein supplements, L-arginine, and certain herbal products can all push creatinine readings higher. Understanding which supplements affect this lab value, and whether the change is cosmetic or concerning, can save you from unnecessary worry after routine bloodwork.
Creatine Monohydrate
Creatine is the single most common supplement linked to elevated creatinine on blood tests. The connection is straightforward: your muscles store creatine and naturally break it down into creatinine, which then enters your bloodstream and gets filtered by your kidneys. When you take supplemental creatine, you increase the pool of creatine in your muscles, and more of it converts to creatinine as a byproduct. A case report in BMJ Case Reports showed that creatine monohydrate caused a significant spike in serum creatine but only a marginal increase in serum creatinine, meaning the effect on lab values is real but often modest.
The practical problem is that doctors use creatinine to estimate your kidney filtration rate (eGFR). If creatine supplementation raises your creatinine, your eGFR calculation drops, potentially flagging you as having reduced kidney function when your kidneys are perfectly fine. Research on bodybuilders found that creatine use caused high creatinine measurements and falsely low GFR values across the board. This is an artifact of the math, not a sign of kidney disease.
L-Arginine
L-arginine is a lesser-known cause of elevated creatinine that catches many people off guard. It’s a popular over-the-counter amino acid supplement marketed for exercise performance, blood flow, and erectile dysfunction. It also shows up in many pre-workout formulas.
L-arginine raises creatinine because it sits at the beginning of the metabolic pathway that creates creatine in your body. It combines with glycine to form a precursor molecule, which is then converted into creatine, which eventually breaks down into creatinine. So even though you’re not taking creatine directly, you’re feeding your body the raw material to make more of it. A case documented in Cureus tracked a patient whose creatinine climbed from a baseline of 1.33 mg/dL to 1.68 mg/dL while on L-arginine supplementation. After stopping the supplement, creatinine dropped back to 1.16 mg/dL within seven months. Importantly, a second kidney marker called cystatin C stayed normal the entire time, confirming the kidneys were never actually impaired.
High-Protein Supplements
Whey protein, casein, and other protein supplements can nudge creatinine levels upward through two related mechanisms. First, a high-protein diet increases the production of nitrogenous waste products, adding to the metabolic load your kidneys handle. Second, protein-rich foods (especially meat) contain creatine, which your body converts to creatinine. If you’re combining protein shakes with a diet already heavy in chicken, beef, or fish, the cumulative effect on creatinine can be noticeable.
There’s also a longer-term factor: protein supplements support muscle growth, and muscle mass is one of the strongest predictors of baseline creatinine. Reference ranges for healthy adults run roughly 0.65 to 1.22 mg/dL for men and 0.50 to 0.95 mg/dL for women, but these ranges assume average body composition. A muscular person who trains regularly and uses protein supplements will naturally sit at the higher end or slightly above that range without any kidney problem at all.
Herbal Supplements That Damage the Kidneys
The supplements above raise creatinine without harming your kidneys. Some herbal products, however, cause genuinely elevated creatinine because they injure kidney tissue. This is a fundamentally different situation.
The most dangerous example is aristolochic acid, found in plants from the Aristolochia family. These herbs appear in some traditional Chinese medicine formulations and weight-loss capsules. In the 1990s, nine women in Belgium developed kidney failure after taking weight-loss pills containing an Aristolochia species, a condition that became known as Chinese herb nephropathy. Reports of aristolochic acid causing acute kidney failure date back to the 1960s in China.
Other herbal products linked to kidney toxicity include Tripterygium (thunder god vine), which has been found to cause severe damage to kidney tubules, and rhubarb root (Rheum palmatum), whose anthraquinone compounds, including rhein and emodin, can injure the kidneys under certain conditions. These are not mainstream Western supplements, but they circulate in herbal medicine markets and online retailers, sometimes without clear labeling of their ingredients.
Anabolic Steroids and Stacking
Anabolic androgenic steroids aren’t traditional supplements, but they’re widely used alongside them in fitness circles and worth mentioning. Steroids drive rapid muscle growth, and that increased muscle mass generates more creatinine as a natural waste product. On top of that, steroid users frequently take creatine and high-protein supplements simultaneously, compounding the effect. Research comparing bodybuilders who used steroids and dietary supplements to those who didn’t found significantly higher creatinine and lower estimated kidney function scores in the users, though much of the difference was attributed to the measurement artifact rather than true kidney decline.
Why Standard Blood Tests Can Mislead You
The standard creatinine blood test measures one molecule and uses it to estimate how well your kidneys filter blood. That estimate breaks down when anything other than kidney function changes the amount of creatinine in your blood. Muscle mass, diet, and the supplements described above all do exactly that. Older lab methods (the alkaline picrate assay) were even more unreliable, producing inaccurate readings in the presence of substances like vitamin C, glucose, and excess protein. Newer enzymatic assays are more specific, but they still can’t distinguish between creatinine from supplement metabolism and creatinine that’s accumulating because your kidneys aren’t clearing it.
If your creatinine comes back high and you take any of the supplements listed here, the most useful next step is a cystatin C test. Cystatin C is a small protein produced at a steady rate by nearly every tissue in your body. Unlike creatinine, it isn’t influenced by muscle mass, diet, or amino acid supplementation. It gets freely filtered by the kidneys and broken down afterward, making it a much more reliable gauge of actual kidney function in people who are muscular, athletic, or supplement-heavy. Studies consistently show that cystatin C displays far less variability than creatinine across different body compositions and doesn’t fluctuate dramatically even in bodybuilders using multiple supplements.
Getting Accurate Results
If you know you have bloodwork coming up and want the most accurate creatinine reading, stop taking creatine and L-arginine ahead of time. Most clinicians suggest discontinuing creatine for at least three to four weeks before testing, since it takes time for your body to clear the extra creatine stores in muscle and for creatinine production to return to baseline. In the L-arginine case report, creatinine was still normalizing a week after stopping and didn’t fully settle for several months, though most of the drop happened in the first few weeks.
Reducing protein intake to more moderate levels (closer to 0.8 to 1.0 grams per kilogram of body weight) for a few days before the test can also help, since a large protein meal the night before bloodwork can temporarily raise creatinine. If stopping supplements isn’t practical, or if your results still look off, asking for a cystatin C measurement alongside creatinine gives your doctor a much clearer picture of whether your kidneys are actually under stress or your lab values are simply reflecting what you take.