Creatine monohydrate, one of the most widely studied sports supplements, does not directly cause body odor in most people who take it. The compound itself is nearly odorless, and its primary metabolic byproduct, creatinine, shows up in sweat at very low concentrations. Yet the question persists in gym forums and supplement reviews, and it is not entirely without basis. The explanation involves a tangle of gut bacteria, liver enzymes, skin microbes, and a case of mistaken identity with a closely named but very different supplement.
What Your Body Does with Creatine
When you take creatine monohydrate, most of it ends up stored in your muscles as phosphocreatine, where it helps regenerate the energy molecule ATP during short bursts of effort. The portion your body doesn’t use gets broken down into creatinine, a waste product that your kidneys filter out through urine. A small fraction of creatinine does leave through sweat, but research on sweat composition shows that the concentration of creatinine in sweat fluid is low and doesn’t change much with the seasons or with kidney workload.1PubMed. Sweat urea, uric acid and creatinine concentrations in uraemic patients Creatinine itself is essentially odorless at these trace levels, so the creatine-to-creatinine pathway is not the source of any smell you might notice.
Newer wearable sweat sensors can now detect creatinine alongside chloride and other biomarkers in real time, and the amounts they measure are used as indicators of kidney function rather than as warning signs of odor-producing concentrations.2Advanced Functional Materials. Soft, Skin‐Interfaced 3D Microfluidic Systems for High Performance Assessment of Sweat Rate, Cumulative Loss and Biochemical Content In short, the metabolic waste your body produces from creatine doesn’t smell, and the amount that reaches your skin surface is tiny.
The Trimethylamine Question
If creatine’s own breakdown products are odorless, where does the smell rumor come from? A likely suspect is a compound called trimethylamine, or TMA, which has a notoriously pungent, fishy odor. Gut bacteria produce TMA from dietary precursors like choline and carnitine, both of which are abundant in red meat, egg yolks, and full-fat dairy products.3PubMed Central. The dietary source of trimethylamine N-oxide and clinical outcomes: an unexpected liaison The liver then converts most of that TMA into trimethylamine N-oxide (TMAO), which is odorless.4PubMed Central. Gut‒heart axis: emerging therapies targeting trimethylamine N-oxide production
Here is the critical distinction: creatine and carnitine are different molecules. Creatine is not a known dietary precursor to TMA. But people who take creatine often also eat high-protein diets loaded with red meat, eggs, and sometimes L-carnitine supplements. Those foods and supplements feed the gut bacteria that produce TMA. So the smell some creatine users report may have less to do with the creatine itself and more to do with the overall dietary pattern that goes along with heavy supplementation.
When the Liver Cannot Keep Up
Under normal circumstances, a liver enzyme called FMO3 (flavin-containing monooxygenase 3) efficiently converts smelly TMA into odorless TMAO. This enzyme is highly specific to that job and very efficient at it, handling the reaction far faster than any other enzyme in the body.5PubMed. Isoform specificity of trimethylamine N-oxygenation by human flavin-containing monooxygenase (FMO) and P450 enzymes: selective catalysis by FMO3 For most people, TMA gets cleared before it accumulates enough to produce any smell.
But some people carry genetic variants of FMO3 that reduce the enzyme’s effectiveness dramatically. Certain mutations slash its ability to convert TMA by more than 90%, leaving the fishy-smelling compound to build up in sweat, breath, and urine.6PubMed Central. Functional characterization of genetic variants of human FMO3 associated with trimethylaminuria The resulting condition, called trimethylaminuria or “fish odor syndrome,” is rare. Most people who have it know about it long before they start taking any supplement. But milder variants of FMO3 impairment exist along a spectrum. Someone with a partial reduction in FMO3 activity might never notice a problem on a typical diet, yet could develop a faint odor after significantly increasing their intake of TMA precursors through high-protein eating or carnitine supplements taken alongside creatine.
The L-Carnitine Mix-Up
Creatine and L-carnitine are often sold side by side, sometimes even blended together in the same product. Their names sound similar enough that many people confuse them. But their effects on body odor are very different. A published case report documented a patient who developed classic fish odor syndrome while taking supplemental L-carnitine. The odor resolved completely after the carnitine was discontinued. The authors linked the episode to excess carnitine saturating the body’s elimination pathway, likely overwhelming FMO3 capacity.7PubMed. L-carnitine treatment and fish odor syndrome: an unwaited adverse effect
Carnitine is a direct precursor that gut bacteria convert into TMA. Creatine is not. If you are taking a combined supplement that contains both, the carnitine component is the more plausible culprit for any fishy or unusual smell. It is worth checking the label of whatever you are using, because many “creatine blends” include carnitine, betaine, or other ingredients that have their own metabolic effects. Someone blaming creatine for a new body odor may actually be reacting to something else in the same tub.
How Body Odor Actually Works
Fresh sweat from eccrine glands (the ones covering most of your body) is largely odorless. The smell people associate with sweating comes mainly from bacteria on the skin breaking down sweat components into volatile, smelly molecules. In the armpit specifically, certain species of Corynebacterium are the primary culprits. These bacteria transform sweat ingredients into steroid derivatives, short branched-chain fatty acids, and sulfur-containing compounds that produce the characteristic underarm smell.8PubMed. Molecular basis of human body odour formation: insights deduced from corynebacterial genome sequences
Other common skin residents contribute too. Research on body odor in both children and adults found that Staphylococcus epidermidis produces enzymes that convert lactic acid and amino acids into acetic acid and isovaleric acid, a compound with a sharp, sour, sweaty smell. The pathways involved center on pyruvate metabolism and branched-chain amino acid breakdown.9PubMed Central. Understanding the microbial basis of body odor in pre-pubescent children and teenagers None of these bacterial processes are known to be affected by creatine supplementation. The bacteria are feeding on amino acids, fatty acids, and steroids already present in sweat, not on creatinine or creatine.
That said, anything that changes how much you sweat or what is in your sweat can shift the equation. More sweat means more substrate for bacteria. A high-protein diet increases the concentration of amino acids and urea in sweat, giving bacteria more raw material. So someone who starts taking creatine as part of a broader shift toward heavier training and more protein intake may notice changes in their body odor that are real but caused by the training and diet, not the creatine itself.
Gastrointestinal Side Effects and Indirect Odor
Creatine does cause GI discomfort for a surprising number of users. A recent study found that nearly 80% of participants reported at least some GI symptoms over 28 days of supplementation, with bloating, water retention, puffiness, and stomach discomfort being the most common complaints. Participants who used a higher initial loading dose reported more symptoms that they rated as more severe, though the difference did not reach statistical significance.10medRxiv. Gastrointestinal and Fluid Retention Symptoms Associated with Creatine Monohydrate With and Without Loading Dose Over 28 Days of Supplementation
Bloating and stomach discomfort often come with increased gas, and gas can certainly carry its own odor. This is probably the most common way creatine supplementation leads to a genuine smell issue, though users tend to search for “does creatine make you smell” thinking about body odor rather than flatulence. If you are experiencing significant bloating after starting creatine, consider whether a loading phase is driving the problem. Many researchers and coaches now recommend skipping the traditional high-dose loading phase entirely and starting at a lower daily maintenance dose, which achieves full muscle saturation over a few weeks rather than a few days, with fewer gut complaints along the way.
Creatine, Hydration, and Sweat
One widespread claim is that creatine dehydrates you, which could theoretically concentrate waste products in sweat and make it smell worse. The evidence points in the opposite direction. A study of endurance-trained athletes found that creatine supplementation actually increased intracellular water and led to a more efficient thermoregulatory response during exercise in the heat, with reduced heart rate, lower rectal temperature, and a lower sweat rate compared to placebo.11International Journal of Sport Nutrition and Exercise Metabolism. The Effects of Creatine Supplementation on Cardiovascular, Metabolic, and Thermoregulatory Responses during Exercise in the Heat in Endurance-Trained Humans
A separate trial that specifically tested creatine users who were dehydrated and exercising in the heat found no differences in rectal temperature or thermoregulation between creatine and placebo groups, and concluded that short-term creatine supplementation did not compromise hydration status or thermoregulation.12PubMed Central. Creatine use and exercise heat tolerance in dehydrated men So creatine doesn’t appear to dehydrate you or change your sweating pattern in a way that would intensify body odor. If anything, the slight increase in water retention inside cells could dilute sweat rather than concentrate it.
What Is Actually in Your Supplement
Not all creatine products are created equal, and the supplement industry is notoriously loose about quality control. An analysis of commercially available creatine supplements found that roughly 15% of samples contained detectable levels of manufacturing contaminants, including dihydro-1,3,5-triazine and dicyandiamide at concentrations above screening thresholds.13Food Chemistry. Levels of creatine, organic contaminants and heavy metals in creatine dietary supplements While these contaminants are not known to cause body odor specifically, low-quality creatine can have a stronger chemical smell in the container, and people sometimes interpret that as a sign the supplement is affecting their own body chemistry.
Multi-ingredient pre-workout or “creatine complex” products pose a different issue. These often contain added L-carnitine, betaine, choline, or large doses of B vitamins, each of which can affect body odor through independent metabolic routes. Choline, for instance, is converted to TMA by the same gut-bacteria pathway described earlier. High-dose B vitamins change the color and smell of urine. If you started noticing an odor around the same time you started a new supplement, check whether you are actually taking pure creatine monohydrate or a blend with additional ingredients.
Protein Intake and Ammonia
People who take creatine are almost always training hard and eating a lot of protein. High protein intake increases the amount of nitrogen your body needs to dispose of, primarily as urea and ammonia. During intense exercise, when protein is being broken down at higher rates, ammonia can be released through sweat and breath. This gives a sharp, acrid quality to perspiration that people sometimes describe as smelling “like chemicals” or “like cat urine.”
This is not a creatine effect. It happens to anyone pushing hard enough on a high-protein diet, supplement or not. But because the creatine and the protein ramp-up often happen at the same time, the creatine gets the blame. A practical way to test this is to keep your diet and training the same while stopping creatine for a couple of weeks. If the smell doesn’t change, protein metabolism or your skin microbiome is the more likely explanation.
Who Might Actually Notice a Change
For the vast majority of creatine users, no odor change will occur. But a few specific situations raise the odds:
- Partial FMO3 impairment: If you happen to carry a milder genetic variant of FMO3, you may have less capacity to neutralize TMA. Normally this causes no problems, but adding a heavy protein and carnitine load on top could tip the balance toward a detectable fishy smell.
- Combined supplements: If your product contains L-carnitine, choline, or betaine alongside creatine, those ingredients are known TMA precursors and can cause odor in susceptible individuals.
- GI disruption: If creatine causes significant bloating and gas for you, that can produce noticeable odor, particularly during and after the loading phase.
- Dramatic diet shifts: Starting creatine as part of a broader move to a very high-protein, high-red-meat diet increases ammonia and TMA precursors simultaneously.
In each of these cases, the fix is specific and doesn’t require stopping creatine. Switching to pure creatine monohydrate without carnitine, skipping the loading phase, moderating protein sources, or addressing the underlying diet usually resolves whatever odor issue appeared.
The Smell of Gym Clothes
There is one more angle worth mentioning: the smell that clings to athletic wear. Synthetic fabrics trap bacteria and the volatile fatty acids they produce far more stubbornly than cotton or merino wool. Someone who starts taking creatine is usually also training more frequently, accumulating more sweaty synthetic gear, and possibly reusing items between washes. The resulting funk is real and can be dramatic, but it is a laundry problem, not a supplement problem. Bacteria embedded in polyester fibers continue breaking down trapped sweat residues even after a garment dries, which is why a shirt can smell fine out of the dryer and then bloom into a stench the moment you start to warm up again. Washing in hot water, using enzyme-based detergents, and replacing heavily used synthetic gear periodically addresses the issue more effectively than any change to your supplement stack.