Benefits
Energy and less fatigue
In a 364 person trial in people with cancer-related tiredness, 2,000 mg a day of American ginseng improved fatigue scores more than placebo at 8 weeks, though not at the 4 week main endpoint. A 65 person trial of 250 mg a day of Asian ginseng extract also lowered fatigue in 4 weeks. In 90 adults with unexplained chronic tiredness, total fatigue scores did not beat placebo, though mental fatigue did.
Mental performance
A Cochrane review of 9 trials found no convincing evidence that Asian ginseng improves thinking in healthy people; some measures improved, but results were too varied to pool, so the evidence is inconclusive. In a later 3 week trial in 149 stressed adults, 200 mg a day of red ginseng powder gave faster responses than placebo on one planning task.
Immune function and antibody response
In 279 adults prone to colds, an American ginseng extract taken for 4 months over flu season meant fewer colds per person and fewer days with symptoms than placebo. In 227 adults given a flu shot, 100 mg a day of a standardized Asian ginseng extract for 12 weeks raised antibody levels and natural killer cell activity, and fewer flu or cold cases were reported than on placebo.
Stress and mood
In 149 moderately stressed adults, 200 mg a day of red ginseng powder for 3 weeks lowered perceived stress and negative mood scores more than placebo, with only a borderline change in depression scores. The product's funder took part in designing the study. This is a single short trial, so the effect on everyday stress is not settled.
Fasting blood sugar
A pooled analysis of 16 randomized trials lasting at least 30 days found that ginseng lowered fasting blood glucose by a small 0.31 mmol/L (about 6 mg/dL) versus control in people with and without diabetes, with no significant overall change in fasting insulin, HbA1c or insulin resistance. Most of the trials lasted under 12 weeks.
Mechanism of action
Two groups of active compounds
Ginseng root contains ginsenosides, a family of saponins such as Rb1 and Rg1, and polysaccharides. Products differ in which they emphasise: the American ginseng extract tested against colds was rich in polysaccharides, while the red ginseng tested for stress supplied 24 mg of ginsenosides a day. That variation is one reason trial results differ.
Immune cell activity
In a 12 week trial in adults given a flu shot, a standardized Asian ginseng extract roughly doubled natural killer cell activity versus placebo and raised vaccine antibody levels. These are measured immune markers; how much they explain the lower number of colds reported is not established.
Antioxidant markers
In a 4 week trial in adults with chronic tiredness, Asian ginseng extract lowered blood markers of oxidative stress (reactive oxygen species and malondialdehyde) versus placebo, and the lower dose raised glutathione. The authors proposed this as part of its effect on fatigue, which remains a hypothesis.
Clinical trials
Randomized, double-blind, placebo-controlled trial (N07C2) at 40 institutions testing 2,000 mg a day of Wisconsin-grown American ginseng (Panax quinquefolius) for 8 weeks (Barton et al. 2013, J Natl Cancer Inst).
364 fatigued cancer survivors, some still in active cancer treatment.
The main endpoint, general fatigue at 4 weeks, did not reach significance (change 14.4 versus 8.2 points, P = 0.07). At 8 weeks the improvement was significantly larger with ginseng (20 versus 10.3 points, P = 0.003), with greater benefit in people receiving active treatment. Side effects did not differ from placebo.
Randomized, double-blind, placebo-controlled trial of 250 mg a day of standardized Panax ginseng extract for 4 weeks, registered as IRCT2017101536777N1 (Rahmani et al. 2026, Support Care Cancer).
65 survivors of gastrointestinal cancers, at least 4 months after treatment, with moderate to severe fatigue.
Fatigue scores after 4 weeks were lower with ginseng than placebo (3.99 versus 5.37 on the Brief Fatigue Inventory, adjusted difference 1.38 points, p < 0.001), and general activity, walking ability, mood and enjoyment of life also improved. No treatment-related adverse events were reported. It was a short trial.
Randomized, double-blind, placebo-controlled parallel trial of a 20% ethanol extract of Panax ginseng at 1 g or 2 g a day for 4 weeks (Kim et al. 2013, PLoS One).
90 adults (21 men, 69 women) with idiopathic chronic fatigue.
The total fatigue score fell but did not differ significantly from placebo (P>0.05). Mental fatigue scores improved significantly with both doses, and only the 2 g dose lowered the visual analogue fatigue score versus placebo. Oxidative stress markers fell versus placebo.
Randomized, double-blind, placebo-controlled trial of two capsules a day of a polysaccharide-rich North American ginseng extract for 4 months, starting at the onset of flu season (Predy et al. 2005, CMAJ).
323 adults aged 18 to 65 with at least 2 colds in the previous year; 279 who started treatment were analysed (130 ginseng, 149 placebo).
Colds per person were lower with ginseng (0.68 versus 0.93), fewer people had 2 or more confirmed colds (10.0% versus 22.8%), and total symptom scores and days with cold symptoms were lower (10.8 versus 16.5 days).
Multicentre, randomized, double-blind, placebo-controlled trial of 100 mg a day of the standardized Panax ginseng extract G115 for 12 weeks, with a flu vaccination at week 4 (Scaglione et al. 1996, Drugs Exp Clin Res).
227 volunteers attending 3 private practices in Milan (114 ginseng, 113 placebo).
Cases of flu or colds between weeks 4 and 12 numbered 15 with ginseng versus 42 with placebo (p < 0.001). Antibody levels at week 8 averaged 272 versus 171 units, and natural killer cell activity was nearly twice as high with ginseng. Safety blood tests did not change, and there were 9 adverse events in total, mainly insomnia. It is an older trial.
Randomized, double-blind, placebo-controlled trial of 200 mg a day of hydroponically grown red Panax ginseng root powder (24 mg ginsenosides) for 3 weeks; the funder took part in designing the study (Dormal et al. 2025, Nutrients).
149 moderately stressed adults (72 ginseng, 77 placebo).
Perceived stress and negative mood scores fell significantly more with ginseng than with placebo, and responses were faster on one spatial planning task. The drop in depression scores was only marginally larger than with placebo.
Randomized, double-blind, placebo-controlled 4 week trial in which participants took warfarin for 3 days in weeks 1 and 4 and American ginseng or placebo from week 2 (Yuan et al. 2004, Ann Intern Med).
20 healthy young volunteers.
After 2 weeks of ginseng, peak INR fell versus placebo (difference 0.19, P = 0.0012), and warfarin blood levels were also lower, meaning ginseng weakened warfarin's effect. The volunteers were not patients on long-term warfarin.