Testosterone Booster Side Effects and Who Should Skip Them
"Natural" is not a safety rating. In my guide on whether testosterone boosters work I only touched on safety. This article goes deeper, using the best sources I could find. I'm not a doctor, and this is not medical advice. Your own doctor knows your history and your medications, and I don't.
What do the trials say about side effects?
Mostly reassuring, with a big asterisk. A 2026 review of fenugreek trials found that among the studies that reported serious adverse events, none had any. But the same authors said that side-effect reporting was often unclear, the studies were small and short, and long-term safety remains uncertain (Yang et al., 2026). The NIH says much the same about ashwagandha: it may be safe in the short term, up to 3 months, and there isn't enough information to reach conclusions about long-term safety (NCCIH).
There is also a built-in problem with small trials. A rare side effect simply won't show up in a group of 50 or 100 people.
That is one reason rare problems, like liver injury, tend to show up as case reports once a product is already on the shelf.
What is known about each ingredient?
| Ingredient | What is known | Ask your doctor first if you... |
|---|---|---|
| Ashwagandha | The NIH calls it rare, but a number of cases link ashwagandha supplements to liver injury. It may interact with several types of medication. | Have liver disease, a thyroid or autoimmune condition, or surgery coming up. Take medicine for diabetes or high blood pressure, immunosuppressants, sedatives, anti-seizure drugs or thyroid medicine. |
| Fenugreek | The NIH lists diarrhea, nausea and other digestive symptoms. Large doses may cause a harmful drop in blood sugar. It can cause allergic reactions, including serious ones. | Have diabetes, have allergies, or take any medicine. |
| Tongkat ali | I did not find solid long-term safety data in the sources I used. | Take prescription medication or have a hormone-sensitive condition. |
| D-aspartic acid | Long-term safety is not well studied. | Take prescription medication or have any health condition. |
| Zinc, vitamin B3, magnesium | Added to many booster formulas. In one review, 13 of 50 products went over the FDA's upper limit for zinc, vitamin B3 or magnesium. | Already take a multivitamin or other mineral supplements. |
Can testosterone boosters hurt your liver?
The best-documented case is ashwagandha. A case series from Iceland and the US Drug-Induced Liver Injury Network described five people with liver injury attributed to ashwagandha supplements. All developed jaundice, along with symptoms like nausea, lethargy, itching and abdominal discomfort, 2 to 12 weeks after starting. Liver tests returned to normal within 1 to 5 months in four of them, and none developed liver failure. Chemical analysis confirmed ashwagandha in the products and found no other toxic compounds, although in one case a second herb, rhodiola, was a possible contributor (Björnsson et al., 2020).
A later series from India was less reassuring. Of 8 patients with liver injury from single-ingredient ashwagandha products, 5 had underlying chronic liver disease, and 3 developed acute-on-chronic liver failure and died. The authors concluded that ashwagandha liver injury can be fatal in people with pre-existing liver disease (Philips et al., 2023).
These are case reports, so they can't tell us how often it happens. The NIH calls it rare. But they are the reason I would not take ashwagandha with a liver condition unless my doctor agreed.
Can a booster contain drugs that are not on the label?
It has happened in this corner of the supplement world. In an analysis of the FDA's database of tainted products, 776 supplements flagged between 2007 and 2016 contained unapproved drug ingredients. Most were sold for sexual enhancement, weight loss or muscle building, and 89.1% of the muscle-building ones contained synthetic steroids or steroid-like ingredients (Tucker et al., 2018). That does not mean most boosters are tainted. It does mean the label may not tell the whole story, which is one reason to read it closely. I explain how in my label guide.
Who should skip boosters, or ask a doctor first?
- Anyone with a liver condition, or who has had unexplained jaundice. Skip ashwagandha unless your doctor agrees.
- Anyone with a thyroid or autoimmune disorder. The NIH says ashwagandha is not recommended for them.
- Anyone about to have surgery. The NIH says the same for ashwagandha. Tell your surgeon about every supplement you take.
- Anyone on medication. This includes drugs for diabetes and high blood pressure, immunosuppressants, sedatives, anti-seizure medication and thyroid hormones. The NIH lists these as possible interactions with ashwagandha, and for fenugreek its advice is to talk to your provider if you take any medicine.
- Anyone with diabetes. Large fenugreek doses may drop blood sugar.
- Anyone with allergies. Fenugreek can cause serious allergic reactions in some people.
- Anyone pregnant or breastfeeding. The NIH says ashwagandha should be avoided, and fenugreek is not safe in pregnancy in amounts greater than those found in food.
- Anyone being treated for low testosterone, or taking other hormones. Your doctor decides what combines safely.
- Anyone who hasn't been tested. If you don't know your level, you don't know whether there is anything to fix. See how to get tested.
When should I stop and call a doctor?
- Yellowing of the skin or eyes, dark urine, itching, nausea or abdominal pain. These are the symptoms in the ashwagandha liver cases. Stop the product and get seen.
- Hives, swelling or trouble breathing. That is a possible serious allergic reaction. Get emergency care.
- Anything new that worries you after starting a supplement. Bring the bottle, so your doctor can read the label.
You can also report a problem to the FDA through its SmartHub or by phone at 1-888-INFO-FDA.
How do I lower the risk if I still want to try one?
- Get a morning blood test first, and talk to your doctor or pharmacist about what you already take.
- Try one product at a time. If something goes wrong, you'll know what caused it.
- Choose a full label. Every ingredient with its own dose, no "proprietary blend" hiding the headline ingredient, and no vitamin or mineral megadoses.
- Pick a named manufacturer with third-party testing. That is about quality, not proof it works.
- Stay within the doses the studies used, and don't stack several products with overlapping ingredients.
- Stop and see a doctor if you notice any of the signs above.
Frequently asked questions
Do testosterone boosters have side effects?
Trials of herbal ingredients report few side effects, but they are small and short. The NIH lists digestive upset for fenugreek, and liver injury cases have been linked to ashwagandha. Side effects also depend on what else is in the product.
Can testosterone boosters damage your liver?
Case reports link ashwagandha supplements to liver injury. The NIH calls it rare. In one series most people recovered within months, but in an Indian series people with existing liver disease died. If you have a liver condition, ask your doctor before using any herbal booster.
Are testosterone boosters safe to take every day?
Nobody knows for sure. Trials last weeks to a few months, and the NIH says there is not enough information to reach conclusions about the long-term safety of ashwagandha. Fenugreek reviews say the same about long-term safety.
Can a testosterone booster contain hidden drugs?
Some supplements have. The FDA flagged 776 supplements for hidden drug ingredients from 2007 to 2016, mostly products sold for sexual enhancement, weight loss or muscle building. Most boosters aren't in that group, but the risk is real enough to read the label closely.
Who should not take a testosterone booster?
People with liver, thyroid or autoimmune conditions, people about to have surgery, people with diabetes or allergies, anyone on medication, and anyone pregnant or breastfeeding should talk to a doctor first. If you haven't had a blood test, start there.
Sources
- Yang P, Niu Z, Guo J, Huang T, Chang D, Huang X. Effects of oral fenugreek-derived preparations on testosterone-related outcomes in adult men: a systematic review and meta-analysis of randomized placebo-controlled trials. Front Nutr. 2026;13:1903508. doi:10.3389/fnut.2026.1903508
- National Center for Complementary and Integrative Health. Ashwagandha: what you need to know. nccih.nih.gov
- National Center for Complementary and Integrative Health. Fenugreek. nccih.nih.gov
- Björnsson HK, Björnsson ES, Avula B, et al. Ashwagandha-induced liver injury: a case series from Iceland and the US Drug-Induced Liver Injury Network. Liver Int. 2020:825-829. doi:10.1111/liv.14393
- Philips CA, Valsan A, Theruvath AH, et al. Ashwagandha-induced liver injury: a case series from India and literature review. Hepatol Commun. 2023. doi:10.1097/hc9.0000000000000270
- Tucker J, Fischer T, Upjohn L, Mazzera D, Kumar M. Unapproved pharmaceutical ingredients included in dietary supplements associated with US Food and Drug Administration warnings. JAMA Netw Open. 2018;1(6):e183337. doi:10.1001/jamanetworkopen.2018.3337
- Clemesha CG, Thaker H, Samplaski MK. "Testosterone boosting" supplements composition and claims are not supported by the academic literature. World J Mens Health. 2020:115-122. doi:10.5534/wjmh.190043
- US Food and Drug Administration. FDA 101: Dietary Supplements. fda.gov
Marcus Hale
Writer at The Male Ledger. Not a doctor.
I write about testosterone, energy and vitality after 40, and I link to the studies so you can check my work. Marcus Hale is a pen name; here is why.