Panax ginseng is the root of a slow-growing plant of Korea and northeast China, used for thousands of years and now one of the most studied herbs there is. American ginseng, Panax quinquefolius, is a related species with a different ginsenoside profile. Red ginseng is the same root steamed and dried.

With 57 randomized trials counted by 2009 and several Cochrane reviews since, the shape of the evidence is clear even where the answers are not: small effects on fatigue, memory and erectile function that are consistent in direction, trials of mixed quality, and an umbrella review that rated the meta-analyses themselves poorly. It is a modest herb with a large reputation.

The active constituents are ginsenosides, triterpene saponins of which dozens are characterized, with different species and processing giving different profiles. Proposed actions include nitric oxide release in vascular tissue (the erectile rationale), modulation of the hypothalamic-pituitary-adrenal stress response (the adaptogen rationale), and effects on glucose uptake and on neurotransmission. The mechanisms are plausible and well studied in cells and animals; which of them produces the small human effects is not established.

Erectile function. The 2021 Cochrane review of nine trials in 587 men with mild to moderate erectile dysfunction found a 3.52-point improvement on the IIEF erectile function domain (low certainty) and 2.39 on the IIEF-5 (moderate certainty), both below the minimal clinically important difference, which the review calls a trivial effect. Men were more likely to report ability to have intercourse (risk ratio 2.55, low certainty). Follow-up was 12 weeks at most.

Cognition. A 2024 meta-analysis of 15 trials in 671 people found a small improvement in memory (SMD 0.19, larger at high doses) and no effect on overall cognition, attention or executive function. The 2010 Cochrane review found nine trials, mostly in healthy people, and could pool only five.

Fatigue. A 2018 systematic review of ten studies in people with chronic illness found modest evidence of benefit and a low risk of adverse events, and called it a promising treatment needing stronger trials.

The wide view. A 2011 systematic review of 57 randomized trials found strong evidence for glucose metabolism, psychomotor function and pulmonary disease, and evidence that it does not enhance physical performance. A 2023 umbrella review of 19 meta-analyses found benefit reported for fatigue, physical function, sexual function, menopausal symptoms, metabolic and inflammatory markers, angina and respiratory disease, and rated five of the meta-analyses low quality and 14 critically low.

The umbrella review's summary is representative: gastrointestinal symptoms and potential bleeding, no serious adverse events. The Cochrane erectile review found little or no difference in adverse events from placebo. The 2011 review of 57 trials found a generally good safety profile and low incidence of adverse effects.

The cautions are interactions and pregnancy. Ginseng has been reported to affect warfarin and blood sugar, so anyone on anticoagulants or diabetes drugs should say so to whoever prescribes. A 2008 systematic review found no adverse effects in a pregnancy cohort but recommended caution in the first trimester and during breastfeeding, noting the old androgenization report was due to an adulterant rather than ginseng. Adulteration and ginsenoside content vary widely between products.

A dietary supplement in the United States and sold freely as a food and supplement across Europe and Asia. In some European countries ginseng products are registered as traditional herbal medicines for fatigue, a status that attests to traditional use rather than proof of efficacy. In Korea red ginseng is a regulated functional food. No regulator has licensed it for erectile dysfunction or cognition.