Yes, testosterone does increase creatinine levels. The rise is typically modest, showing up within three months of starting testosterone therapy and peaking around six months. In most cases, this reflects increased muscle mass rather than actual kidney damage, but the distinction matters because it can make your kidney function appear worse than it really is on standard lab tests.
Why Testosterone Raises Creatinine
Creatinine is a waste product your muscles produce constantly. The more muscle you have, the more creatinine ends up in your blood. Testosterone is one of the most powerful signals your body has for building muscle, so when testosterone levels go up, muscle mass follows, and creatinine rises as a direct consequence.
This isn’t limited to people taking testosterone as medication. Anyone with naturally higher testosterone levels tends to have higher creatinine. It’s the main reason men generally have higher creatinine values than women. When someone starts testosterone therapy, whether for low testosterone or as part of gender-affirming care, their creatinine shifts upward as their body composition changes.
How Much Creatinine Increases
Research on transgender men starting testosterone therapy provides some of the clearest data on this effect, since these individuals serve as their own before-and-after comparison. In a matched pair analysis, creatinine values rose by an average of 0.14 mg/dL at three months, 0.21 mg/dL at six months, and 0.15 mg/dL at twelve months compared to baseline. All of these increases were statistically significant.
To put that in context, a typical creatinine range for women is roughly 0.6 to 1.1 mg/dL and for men about 0.7 to 1.3 mg/dL. A jump of 0.15 to 0.21 mg/dL can easily push someone from a “normal” result into a range that looks borderline or flagged, even though nothing is wrong with their kidneys. The shift begins as early as three months and generally reflects the trajectory of muscle gain during that period.
When the Rise Doesn’t Mean Kidney Trouble
Creatinine is the default marker doctors use to estimate how well your kidneys filter blood. The standard formula, called CKD-EPI, plugs in your creatinine level along with your age and sex to calculate an estimated glomerular filtration rate (eGFR). Higher creatinine produces a lower eGFR, which on paper looks like declining kidney function.
A 2025 meta-analysis examined this exact problem in people starting testosterone therapy. The pooled data showed a statistically significant drop in eGFR at both six and twelve months. But blood urea nitrogen (BUN), a separate waste product that kidneys filter and that isn’t tied to muscle mass, did not change at all. None of the included studies reported adverse kidney events. The authors concluded that the eGFR decline was likely not clinically relevant and instead reflected the math of plugging a higher creatinine number into the formula.
This is an important distinction. If your kidneys were actually struggling, you’d expect BUN to rise alongside creatinine. When creatinine goes up but BUN stays flat, the most likely explanation is that your body is simply producing more creatinine from more muscle.
A More Reliable Kidney Marker
For people on testosterone therapy who need accurate kidney monitoring, cystatin C is a better option. Unlike creatinine, cystatin C is produced by nearly all cells in the body at a relatively constant rate. It isn’t influenced by muscle mass, body composition, or testosterone levels.
A study in the American Journal of Men’s Health specifically compared the two markers in men with testosterone-induced muscle growth. Cystatin C showed minimal variability across different body sizes, while creatinine fluctuated significantly with higher BMI and body fat percentage. The researchers concluded that cystatin C more accurately reflects actual kidney function in this population. If you’re on testosterone and a routine blood panel flags your creatinine or eGFR, asking for a cystatin C test can help clarify whether the result is a muscle mass artifact or a genuine concern.
When Testosterone Can Genuinely Affect the Kidneys
The muscle mass explanation covers most cases, but testosterone can affect kidney function through other pathways. Animal research has shown that testosterone increases sodium reabsorption in the kidneys, meaning the body holds onto more salt and water. In studies on hypertensive rats, testosterone reduced sodium excretion by up to 84% and accelerated the development of high blood pressure, rising about 5 mmHg per week. Over time, the combination of elevated blood pressure and increased pressure within the kidney’s filtering units (glomeruli) contributed to scarring of kidney tissue.
In humans, there are documented cases where testosterone caused reversible decreases in kidney blood flow. One case report tracked a patient whose creatinine and cystatin C both rose substantially after a single testosterone injection. Because cystatin C rose too, the increase couldn’t be explained by muscle mass changes alone. The patient’s weight didn’t change either, further ruling out a body composition shift. Kidney function partially recovered after the testosterone cleared but did not return to baseline after a second exposure, suggesting real, though limited, impact on kidney perfusion.
These cases tend to involve supraphysiological doses or individuals with pre-existing kidney vulnerability. For most people on standard replacement doses, the risk of direct kidney harm appears low. But it underscores why monitoring matters, especially in the first year.
Other Factors That Stack With Testosterone
If you’re taking testosterone and also using creatine supplements, both will push your creatinine higher independently. Creatine is stored in muscle and breaks down into creatinine at a steady rate. Supplementing with creatine increases the pool of raw material that converts to creatinine, raising blood levels regardless of kidney function. High meat intake has a similar, though smaller, effect since meat contains both creatine and creatinine.
Case reports of kidney concerns in athletes and bodybuilders are frequently confounded by the combination of testosterone (or anabolic steroids), creatine supplements, other supplements, and sometimes pre-existing conditions. Any one of these can inflate creatinine readings, and together they can produce alarming numbers on a lab panel that don’t necessarily reflect kidney disease. If you’re using multiple substances that affect creatinine, mention all of them to your doctor so the results can be interpreted in context.
What This Means for Your Lab Results
If you’ve started testosterone therapy and your next blood panel shows creatinine creeping up or eGFR dropping slightly, the most common explanation is straightforward: you’re building muscle. The timeline fits if you’re three to twelve months into treatment and the change is in the range of 0.1 to 0.2 mg/dL.
A few signals suggest the change might be more than muscle. If BUN rises alongside creatinine, if you develop swelling or changes in urine output, or if the creatinine jump is large and sudden, those warrant closer investigation. A cystatin C-based eGFR can help sort out the ambiguity. For people with pre-existing kidney disease or risk factors like uncontrolled high blood pressure, closer monitoring during the first year of testosterone therapy is especially worthwhile.