Tongkat ali is a Southeast Asian herbal supplement that primarily affects hormone levels, stress response, and physical performance. In clinical trials, it has raised testosterone levels by up to 37% and lowered the stress hormone cortisol by about 16% over four weeks of daily use. Most of its studied effects center on these two hormonal shifts and the downstream changes they produce in mood, body composition, and sexual function.
How It Affects Testosterone and Cortisol
The most consistent finding across tongkat ali research is a shift in the ratio between testosterone and cortisol. In a widely cited trial of 63 adults with moderate stress, four weeks of 200 mg daily reduced salivary cortisol by 16% while increasing testosterone by 37%. That dual effect matters because cortisol and testosterone tend to work against each other. When cortisol stays chronically elevated from stress, it suppresses testosterone production. By lowering one and raising the other, tongkat ali appears to rebalance the hormonal environment rather than simply forcing testosterone higher.
Interestingly, the supplement does not seem to work through the pathway most people would expect. Luteinizing hormone and follicle-stimulating hormone, the two brain signals that tell the testes to produce testosterone, show no significant changes with tongkat ali supplementation. This suggests it isn’t acting like a direct testosterone booster in the classical sense. Instead, researchers believe it operates partly through the body’s stress-response system, which would explain why people under more stress tend to see bigger effects.
Stress, Mood, and Mental State
Beyond the cortisol numbers, tongkat ali supplementation for four weeks improved self-reported feelings of tension, anger, and confusion in that same trial of moderately stressed adults. These aren’t dramatic psychiatric effects. Think of it more as taking the edge off chronic background stress. If you’re sleeping poorly, overworked, or feeling mentally foggy, the cortisol reduction may translate into a noticeable improvement in daily mood and mental clarity. If you’re already relaxed and well-rested, the effect is likely minimal.
Physical Performance and Body Composition
A five-week study in 25 active older adults found that 400 mg of tongkat ali extract daily produced significant increases in muscular strength compared to a placebo. The hormonal shifts, particularly higher testosterone and lower cortisol, create a more favorable environment for building and maintaining muscle. Cortisol is catabolic, meaning it breaks down tissue, while testosterone promotes muscle protein synthesis. Tipping that balance even modestly can make a difference over weeks of consistent training.
That said, the evidence for dramatic physique changes in young, healthy people is thin. Most of the notable results come from older adults, people under significant stress, or those with below-normal testosterone levels to begin with. If you’re a healthy 25-year-old with normal hormones, tongkat ali is unlikely to produce the kind of gains you’d notice in the mirror.
Sexual Function and Fertility
A one-month study in 76 older men with low testosterone showed promising improvements in sexual health markers. Separately, a three-month trial in 75 men who were partners in couples experiencing infertility found that 200 mg daily significantly improved both sperm concentration and sperm motility. The fertility effects required a longer timeline, with meaningful changes appearing around the three-month mark, which aligns with the roughly 74-day cycle of sperm production.
How Long It Takes to Work
The timeline varies depending on what you’re looking for. Cortisol and mood improvements show up within about four weeks in clinical trials. Strength gains have been measured at five weeks. Fertility-related changes take longer, closer to three months. Most studies that found meaningful results used a minimum of four weeks of daily supplementation, so expecting changes within the first week or two isn’t realistic based on the available evidence.
Dosage and What to Look For
Clinical trials have used doses ranging from 100 to 600 mg daily, with 200 mg being the most common dose in stress and hormone studies and 400 mg used in strength research. The majority of published trials used a standardized water extract containing 0.8% to 1.5% eurycomanone, which is the primary active compound in the root. When shopping for a product, that eurycomanone percentage is the most useful quality marker on the label.
One important detail about that active compound: its oral bioavailability is only about 10.5%, meaning your body absorbs roughly one-tenth of what you swallow. The compound is stable in your digestive tract, so stomach acid isn’t destroying it. The problem is poor absorption through the intestinal lining. Blood levels peak about four to four and a half hours after taking a dose, which is relatively slow. This low absorption rate is likely why consistent daily dosing over weeks matters more than any single dose.
Safety Concerns Worth Knowing
Reported side effects in clinical trials are mild, primarily gastrointestinal discomfort and occasional itching. The more serious concern is product quality. Independent testing has found tongkat ali products contaminated with heavy metals like lead and mercury, and some have been adulterated with prescription erectile dysfunction drugs. Without third-party lab testing, there’s no way to verify what’s actually in a given product from the label alone. Look for brands that display certification from independent testing organizations.
In 2021, the European Food Safety Authority flagged tongkat ali root extract for potential DNA damage observed in animal studies and stated that its overall safety has not been fully established. This doesn’t mean the supplement is dangerous at typical doses, but it does mean long-term safety data in humans is limited. Most clinical trials have run for one to six months, so the effects of years of continuous use remain an open question.