Gym Supplements and Sperm: Creatine, Pre-Workout, Protein Powder — and Why SARMs Are a Different Category

Short answer: mainstream gym supplements like creatine and protein powder have very little human fertility research behind them, in either direction, and there's no good evidence that they harm sperm. Pre-workout products are mostly a caffeine question. SARMs and anabolic steroids are a completely different category: they're hormone-active drugs that can suppress sperm production, and FDA lists infertility and testicular shrinkage among the risks of SARMs. If you're trying to conceive, that last group is the one to stop.

Lifters often get lumped together with "supplements bad" advice. That's not useful. The point of this guide is to sort your shelf into three piles: probably fine, measure it, and stop.

The three-pile checklist

Creatine: little data, no clear red flag

Creatine is one of the most studied sports supplements, but nearly all of that research is about strength, muscle and, more recently, brain health. Human studies that measure semen quality or time to pregnancy in creatine users are scarce, and we didn't find a well-designed trial showing either benefit or harm to fertility.

That absence cuts both ways. You'll see creatine pitched as "good for sperm" because sperm use energy, and you'll see forum claims that it causes problems. Neither claim rests on solid human fertility data. If you already use plain creatine monohydrate, there's no strong reason to stop while trying to conceive. Choose a product with third-party certification, skip blends with added stimulants or "anabolic" herbs, and mention it to your clinician.

Protein powder: a quality question, not a sperm question

Protein powder is essentially food. Whether it comes from whey, casein, soy or pea, the protein itself isn't a known fertility problem. (If soy protein is your concern, a 2021 meta-analysis of clinical studies found no effect of soy protein or isoflavones on men's reproductive hormones; talk it through with your clinician if you use a lot of it.)

The real issues are product quality and what else is in the tub:

• Contaminants. Protein powders can contain trace heavy metals, which can come from plant ingredients and soil. Our guide to lead, mercury and cadmium explains why that matters for both partners.
• Add-ins. "Mass gainer" and "anabolic" protein products sometimes include herbal testosterone blends or stimulants. Read the whole label, not just the protein line.
• Certification. Programs such as NSF Certified for Sport test products for banned substances and check label accuracy. That's especially useful in a category where spiking with undeclared ingredients has happened. More on what seals mean in our third-party testing guide.

Pre-workout: do the caffeine math

Most pre-workouts are built around caffeine, often alongside other stimulants. FDA says up to 400 mg of caffeine a day is not generally associated with negative effects in healthy adults. People who are pregnant, trying to become pregnant or breastfeeding are advised to talk with their health care provider about whether they should limit it.

The problem is how fast it adds up. FDA's own figures put a 12-ounce cup of brewed coffee at roughly 113 to 247 mg, and energy drinks at about 54 to 328 mg per 16 ounces. Pre-workout labels vary just as widely. A morning coffee, a pre-workout scoop and an afternoon energy drink can land you well past 400 mg without noticing.

For the fertility side of caffeine, our alcohol and caffeine limits guide covers what the research does and doesn't show for both partners.

Why SARMs and steroids are a different category

Creatine and protein are nutrients. SARMs (selective androgen receptor modulators) and anabolic steroids are hormone-active drugs. That changes everything.

What FDA says about SARMs

According to FDA's consumer update on SARMs:

• SARMs are not FDA approved for any use.
• They can't legally be marketed in the U.S. as dietary supplements, and are considered unapproved drugs even when sold as supplements.
• They're often sold as supplements or "for research use only," frequently with no warnings on the label.
• Listed risks include heart attack and stroke, liver injury, psychosis, sexual dysfunction, infertility and testicular shrinkage.

How androgens suppress sperm

Your brain releases two hormones, LH and FSH, that tell the testes to make testosterone and sperm. When you take testosterone, steroids or other androgen-like compounds from outside, the brain senses plenty of androgen and turns those signals down. Testosterone in the blood can look high while testosterone inside the testes, and sperm production with it, falls. This is why testicles can shrink on a cycle, and why prescription testosterone is generally avoided in men trying to conceive. howtohaveababy.com explains the mechanism in its testosterone and fertility myth piece.

FDA's broader warning on bodybuilding products notes that some are illegally spiked with steroids or steroid-like substances, and lists testicular shrinkage and sexual dysfunction among the serious reactions. You can be exposed without intending to, which is another reason certification matters.

If you've used SARMs or steroids

• Stop, and tell your clinician exactly what you took and for how long. This isn't a moral judgment; it changes how your results are read.
• Get a semen analysis. If results are abnormal, conceiveguide.com's guide to next steps after an abnormal semen analysis walks through what comes next.
• Recovery takes time and varies from person to person. Don't self-treat with "post-cycle therapy" drugs bought online; recovery should be managed by a clinician.

Training itself: mostly good news

Regular exercise is generally linked to better metabolic health, which supports fertility for both partners. Intensity and volume are where questions start, and we cover them in how exercise intensity affects fertility and finding the right exercise balance. fertilestart.com's male fertility lifestyle guide covers the everyday basics.

Your pre-conception gym checklist

1. Stop SARMs, steroids, prohormones and non-prescribed testosterone.
2. Keep creatine and protein if you like them; switch to third-party-certified products.
3. Add up daily caffeine from all sources, including pre-workout, and discuss your total with your clinician.
4. Remove "test booster" blends, or at least stop stacking them. See our tongkat ali vs. tribulus breakdown for what those herbs actually showed.
5. Get a baseline semen analysis, and repeat it about three months after changes.
6. Know the evaluation timeline: ASRM recommends an infertility evaluation after 12 months of trying if the female partner is under 35, or after 6 months if she's 35 or older.

Supplements don't treat infertility, and none of the products above is a fertility aid. Clear your supplement list with a clinician.

Sources

• FDA. FDA warns of use of selective androgen receptor modulators (SARMs) among teens, young adults. fda.gov
• FDA. Caution: bodybuilding products can be risky. fda.gov
• FDA. Spilling the beans: how much caffeine is too much? fda.gov
• Reed KE, Camargo J, Hamilton-Reeves J, et al. Neither soy nor isoflavone intake affects male reproductive hormones: an expanded and updated meta-analysis of clinical studies. Reprod Toxicol. 2021;100:60–67. PubMed 33383165
• ASRM Practice Committee. Definition of infertility: a committee opinion (2023). asrm.org (PDF)