Ginseng Side Effects: What the Evidence Shows

Ginseng is among the best-known herbal remedies in the world, used for energy, stamina and mental performance. Most people tolerate it well in short courses, but it is not free of side effects or interactions. Our editorial team reviews what has been reported in trials and case reports, and how to use ginseng more safely.

Types of ginseng and why they differ

The word ginseng covers several different plants. Asian or Korean ginseng (Panax ginseng) and American ginseng (Panax quinquefolius) are true ginsengs containing active compounds called ginsenosides. Siberian ginseng (Eleutherococcus senticosus) belongs to a different genus and has a different chemical profile.

Ginsenoside content varies between species, the age of the root, the part of the plant used and processing methods. Red ginseng, for example, is steamed before drying, which changes its ginsenoside composition compared with white ginseng.

These differences matter for side effects. Asian ginseng is traditionally regarded as more stimulating, while American ginseng is considered milder. Products labelled only as 'ginseng' without the species or standardisation make it hard to predict effects.

In the UK, some ginseng products are registered under the Traditional Herbal Registration (THR) scheme run by the MHRA, which means they meet quality standards and carry patient information. Others are sold as food supplements without these safeguards; the THR certification mark helps tell them apart.

Common, mostly mild side effects

In clinical trials, ginseng is generally well tolerated over periods of up to about 12 weeks. The most frequently reported side effects are insomnia and nervousness, particularly with Asian ginseng and with higher doses or evening use.

Headache, digestive upset such as nausea or diarrhoea, and changes in appetite are also reported. These effects are usually mild and resolve after reducing the dose or stopping the product.

Some women have reported breast tenderness or menstrual changes, including post-menopausal bleeding, in case reports. These may reflect weak oestrogen-like activity of some ginsenosides, although the evidence is not conclusive. Any unexpected vaginal bleeding should be assessed by a GP.

Older literature described a so-called ginseng abuse syndrome, with hypertension, nervousness and diarrhoea in long-term heavy users. This report came from an uncontrolled observational study, and many products used then were of uncertain content, so its findings should be interpreted cautiously.

Blood pressure, blood sugar and the heart

Ginseng's effects on blood pressure appear mixed. Some studies show small reductions, others show slight increases, and individual responses vary. People with poorly controlled hypertension should monitor their readings if they decide to try ginseng.

Ginseng, particularly American ginseng, can lower blood glucose after meals. This has been studied as a potential benefit, but for people taking insulin or other diabetes medicines it increases the risk of hypoglycaemia, especially if doses or meal timing change.

Isolated reports describe palpitations and heart rhythm disturbances with ginseng, often in products combined with other stimulants. Anyone with arrhythmias or heart disease should seek medical advice before use.

Drug interactions

The most clinically discussed interaction involves warfarin. A randomised trial in healthy volunteers found that American ginseng reduced warfarin's anticoagulant effect. Anyone on warfarin or other anticoagulants should not start ginseng without speaking to their anticoagulation clinic.

Case reports link ginseng combined with the antidepressant phenelzine, a monoamine oxidase inhibitor, to symptoms such as headache, tremor and mania-like episodes. Caution is generally advised with antidepressants and other psychiatric medicines.

Ginseng may influence the activity of drug-metabolising enzymes, although findings are inconsistent. Its effects on blood glucose also add to those of diabetes medicines. Combining ginseng with caffeine or other stimulants may amplify nervousness and sleep problems.

• Anticoagulants and antiplatelets (warfarin, aspirin, clopidogrel).
• Antidepressants, particularly MAO inhibitors.
• Insulin and oral diabetes medicines.
• Stimulants, including high caffeine intake.
• Immunosuppressants, owing to possible immune-modulating effects.

Who should avoid ginseng and how to reduce risk

Pregnant and breastfeeding women should avoid ginseng. Animal studies have raised concerns about effects of ginsenosides on embryo development, and there are insufficient human safety data.

Children, people with hormone-sensitive cancers, those with autoimmune diseases and people scheduled for surgery should also be cautious. Many surgeons recommend stopping herbal supplements about two weeks before an operation because of potential effects on bleeding and blood sugar.

To reduce risk, choose a product that states the species and standardised ginsenoside content, ideally with a THR mark. Take it in the morning, follow the labelled dose and limit continuous use to a few months, with breaks, as is common in research protocols.

Stop taking it and seek advice if you develop palpitations, severe headache, unusual bleeding or significant changes in mood or sleep. Reporting suspected side effects through the MHRA Yellow Card scheme helps improve safety information for everyone.

Editorial conclusions

Ginseng is usually well tolerated in short courses, with insomnia, headache and digestive upset the most common complaints.

Its effects on blood sugar and potential interactions with warfarin, antidepressants and stimulants are the most important safety concerns.

Choose a clearly labelled product, ideally THR-registered, take it in the morning and avoid it in pregnancy and before surgery.

Our editorial team recommends reading next about Rhodiola as an alternative adaptogen, caffeine and sleep, and how herbal supplements interact with common medicines.

References

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3. Siegel RK. Ginseng abuse syndrome: problems with the panacea. JAMA. 1979;241(15):1614–1615.
4. Coon JT, Ernst E. Panax ginseng: a systematic review of adverse effects and drug interactions. Drug Saf. 2002;25(5):323–344.
5. Vuksan V, Sievenpiper JL, Koo VY, et al. American ginseng (Panax quinquefolius L) reduces postprandial glycemia in nondiabetic subjects and subjects with type 2 diabetes mellitus. Arch Intern Med. 2000;160(7):1009–1013.
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