On side effects, tongkat ali is the safer-studied choice. It has been tested in a number of small human trials with few reported problems. Fadogia agrestis has never been tested in people at all, and its only safety data, from rats, showed signs of harm to the testes. So when you compare fadogia agrestis vs tongkat ali side effects, the honest answer is that one has a modest human safety record and the other has none.
Key takeaways
- Fadogia has zero human trials; tongkat ali has several
- Rat studies linked fadogia to changes in testicular function
- Tongkat ali is usually well tolerated in short trials
- Both carry quality risks: contamination and hidden drugs
Fadogia agrestis vs tongkat ali side effects at a glance
| Fadogia agrestis | Tongkat ali | |
|---|---|---|
| Human trials | None published | Several small RCTs, mostly 4–24 weeks |
| Testosterone evidence | Rats only (5-day study) | Mixed human data; best in stressed or low-T men |
| Main safety concern | Testicular changes in 28-day rat study | Rare liver injury reports; contamination |
| Common side effects | Unknown (anecdotes only) | Occasional stomach upset, headache, rash |
| Established human dose | None | Trials used about 100–600 mg/day of standardized extract |
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What is fadogia agrestis?
Fadogia agrestis is a shrub from West Africa. Its stem has been used in Nigerian folk medicine as an aphrodisiac. It became popular online after podcasts and influencers recommended it for testosterone, often stacked with tongkat ali.
The evidence behind it
Almost everything we know comes from one Nigerian research group working with rats:
- 2005 (Asian Journal of Andrology): Male rats given a water extract of the stem for five days had higher testosterone and more mating behavior than controls.
- 2008 (Journal of Ethnopharmacology, Yakubu et al.): Rats were given 18, 50 or 100 mg/kg of the extract daily for 28 days. At every dose, the researchers saw changes in testicular markers, including higher testes weight and shifts in enzyme and protein levels, which they described as adverse effects on testicular function. Some markers recovered after stopping, mainly at the lowest dose.
- Related rat work from the same group reported changes in liver and kidney markers.
No human study of fadogia, whether a randomized trial, an observational study or even a safety study, has been published. None of the rat findings have been independently replicated.
Fadogia agrestis side effects
Because nobody has studied fadogia in people, its human side effects are genuinely unknown. What we have:
- Testicular concerns. The 28-day rat study is the main red flag. Rat doses don’t translate neatly to people, but it’s a reason for caution, especially for men who want to have children.
- Liver and kidney markers. Changes were reported in rodents, not people.
- User reports. Online reports mention nausea, headaches, poor sleep, irritability and testicular aching, but these are anecdotes from people often taking several supplements at once, so they can’t prove cause.
- Unknown interactions. No one has studied how fadogia interacts with medications.
Some influencers recommend cycling fadogia (for example, a few weeks on and a week off) to reduce risk. That idea isn’t based on any human data.
What is tongkat ali?
Tongkat ali (Eurycoma longifolia) is a Southeast Asian root used traditionally for energy and male vitality. Unlike fadogia, it has been tested in people. Our tongkat ali evidence guide covers the research in depth.
What human studies show
- A 2022 meta-analysis in Medicina (Leisegang et al.) pooled nine studies and found tongkat ali raised total testosterone, with the clearest effects in men with low testosterone. The authors noted the studies were small, varied and showed signs of publication bias.
- A 4-week trial of 63 stressed adults (Talbott 2013) taking 200 mg a day of a standardized extract reported lower cortisol and better mood. Like most tongkat ali trials, it was funded by the extract’s manufacturer.
- 12-week trials in men aged 30–70 using 100–300 mg a day found no clear safety problems on blood tests.
Tongkat ali side effects
In trials, side effects were about as common as with placebo. Reported issues include:
- Stomach discomfort, nausea or diarrhea
- Headache or rash (uncommon)
- Restlessness or trouble sleeping, mostly in user reports rather than trials
More serious, rare concerns:
- Liver injury. NIH’s LiverTox lists tongkat ali as a possible rare cause of liver injury, based on a single case report.
- Drug interactions. In a small study of healthy men, tongkat ali reduced absorption of the blood pressure drug propranolol. Interactions with other drugs haven’t been studied.
- DNA-damage signal. In 2021, the European Food Safety Authority reviewed one water extract and said its safety had not been established, partly because lab tests suggested possible genotoxicity.
- Contamination. Surveys have found mercury and lead in some tongkat ali products, and regulators have recalled tongkat-labeled products containing hidden prescription drugs.
Should you stack fadogia and tongkat ali?
Many men take the two together. There’s no human research on the combination, so its benefits and risks are unknown. If you’re interested in tongkat ali, there’s a reasonable case for trying it on its own, at studied doses, from a third-party-tested brand. Adding fadogia means adding an ingredient with no human safety data.
If you want to compare tongkat ali with a better-studied herb, see our tongkat ali vs ashwagandha comparison. For a broader look at the options, visit our testosterone support hub.
Safety checklist
- Talk to your doctor first if you take medication, have liver or kidney disease, or have a hormone-sensitive condition such as prostate cancer.
- Avoid fadogia if you’re trying to conceive.
- Choose products with third-party testing for heavy metals and undeclared drugs.
- Get a blood test if you suspect low testosterone. Fatigue, low libido and erection problems can have medical causes, and erectile dysfunction can be an early sign of heart disease or diabetes. Our guide to symptoms of low testosterone explains what to ask.
Bottom line: Tongkat ali has a modest but real human safety record and some evidence for testosterone in men with low levels. Fadogia agrestis has no human studies at all, and its only long-term data, from rats, raised concerns about testicular function. If you’re weighing side effects, tongkat ali is the more cautious choice.
Is fadogia agrestis safe?
Nobody knows, because it has never been studied in humans. A 28-day rat study found changes in testicular function at all doses tested, so caution is warranted, especially for men trying to have children.
What are the side effects of tongkat ali?
In trials, side effects were uncommon and similar to placebo. Possible issues include stomach upset, headache, rash and restlessness. Rare liver injury has been reported, and some products have been contaminated with heavy metals.
Can you take fadogia agrestis and tongkat ali together?
Many people do, but the combination has never been studied, so its safety is unknown. Check with your doctor, particularly if you take medication.
Does fadogia agrestis increase testosterone in humans?
There’s no human evidence. The testosterone increase came from a five-day study in rats.