Herb Safety Quick Reference by Group of Medicines and Conditions
A quick reference of herbs and the medicines and conditions they are reported to affect, from blood thinners to pregnancy, with what each source says and links to full profiles.
Content last updated . This page has not been medically reviewed.
Safety first. Natural products can cause side effects and interact with medicines. Read herb safety and interactions before you use anything on this page.
Urgent first. In the US, call 911 for chest pain, trouble breathing, fainting, signs of a stroke, a seizure or a severe allergic reaction after any herbal product. For a possible poisoning, Poison Help is 1-800-222-1222. For a medicine question, ask the prescriber or pharmacist; do not stop or change a prescribed medicine on your own.
How to use this table
NCCIH says dietary supplements may interact with medications, pose risks if you have certain medical problems or before surgery. [1] The tables below group herbs by the medicine or condition that sources link them to. An herb that is not listed is not shown to be safe, since lack of evidence is not proof of safety. The last column says what kind of evidence the source describes, not our own grading. For how interaction evidence is rated, read how interactions work.By group of medicines
| Medicine group | Herbs reported | What the sources say | Type of evidence |
|---|---|---|---|
| Blood thinners (warfarin, aspirin) | Ginkgo, garlic, Asian ginseng | NCCIH says ginkgo may raise bleeding risk with anticoagulants such as warfarin. [2] Garlic supplements may raise bleeding risk, which matters with anticoagulants, aspirin or surgery. [3] Asian ginseng may interfere with blood clotting. [4] | Stated by NCCIH; basis not given |
| Antidepressants and serotonin medicines | St. John's wort, yohimbe | St. John's wort with certain antidepressants may lead to serious serotonin-related side effects. [5] NCCIH says not to use yohimbe with monoamine oxidase inhibitors or tricyclic antidepressants. [6] | Stated by NCCIH |
| Many other medicines | St. John's wort, green tea extract, goldenseal | St. John's wort can weaken many medicines, including birth control pills, cyclosporine and warfarin. [5] Green tea extract can lower blood levels of atorvastatin. [7] Goldenseal extract lowered metformin levels about 25 percent in healthy adults. [8] | Studies in healthy adults for the last two |
| Sedatives, sleep medicines, alcohol | Kava, valerian | Kava should not be used with benzodiazepines or alcohol. [9] Valerian should not be taken with alcohol or sedatives. [10] | Stated by NCCIH |
| Heart, blood pressure and steroid medicines | Licorice root, aloe vera, bitter orange | Licorice (glycyrrhizin) can cause irregular heartbeat and cardiac arrest, mostly with large amounts or long use, and has reported interactions with corticosteroids. [11] Overuse of aloe latex may raise side effects of digoxin. [12] For bitter orange, see stimulant herbs. | Reports; stated by NCCIH |
| Stimulants and caffeine | Ephedra, bitter orange | NCCIH says ephedra might interact with stimulants like caffeine. [13] Bitter orange is often combined with caffeine in weight-loss products. [14] | Theoretical for ephedra, per NCCIH |
By health condition or situation
| Situation | Herbs reported | What the sources say | Type of evidence |
|---|---|---|---|
| Diabetes medicines | Goldenseal, Asian ginseng | Goldenseal lowered metformin levels. [8] Some evidence suggests Asian ginseng might lower blood sugar. [4] | Study in healthy adults; some evidence |
| Liver disease or liver injury | Black cohosh, kava, green tea extract, turmeric, aloe leaf extract, valerian, chaparral, germander | NCCIH reports rare liver injury, some serious, for black cohosh and kava; mainly extract capsules or tablets for green tea; bioavailable formulations of turmeric; acute hepatitis with oral aloe leaf extracts; very rare cases with valerian. [15][9][7][16][12][10] See chaparral and germander. | Case reports |
| Kidney disease | Aristolochic acid herbs, licorice | Aristolochic acid has caused kidney failure. [17] NCCIH links licorice's glycyrrhizin to severe effects in people with heart or kidney conditions. [11] See aristolochic acid. | Cohorts and case reports |
| Surgery | Garlic (and any supplement) | Tell the surgical team about garlic supplements. [3] See herbs before and after surgery. | Stated by NCCIH |
| Allergy | Butterbur, garlic | Butterbur may cause reactions in people allergic to ragweed, chrysanthemums, marigolds and daisies. [18] Some people react to garlic. [3] See allergy and cross-reactivity. | Stated by NCCIH |
| Contamination and mislabeling | Black cohosh, goldenseal, bitter orange, skullcap | Wrong herb found in some black cohosh products. [15] Goldenseal products with unlisted ingredients. [8] Skullcap adulterated with germander. [19] Some bitter orange supplements held synthetic amines. [20] See quality testing. | Product analyses |
Pregnancy, breastfeeding and children
| Herb | What the sources say |
|---|---|
| Ephedra | Considered unsafe in pregnancy, breastfeeding and for children. [13] |
| St. John's wort | May be unsafe in pregnancy. [5] |
| Goldenseal | Should not be used in pregnancy or breastfeeding, nor given to infants. [8] |
| Comfrey, coltsfoot, butterbur with PAs | Children are particularly vulnerable to PAs. [21] PA-containing butterbur should not be used in pregnancy or breastfeeding. [18] See pyrrolizidine alkaloids. |
| Yohimbe | May be unsafe by mouth in pregnancy or breastfeeding. [6] |
| Ginkgo | May be unsafe in pregnancy. [2] |
| Black cohosh | May not be safe in pregnancy or breastfeeding. [15] |
| Asian ginseng | Some experts recommend against use for infants, children and pregnant or breastfeeding women. [4] |
See herbs during pregnancy and herbs for children and teens.
Limits of this page
It covers only herbs for which we read a source this session, and it is not a complete interaction checker. For checking tools, see how to check herb interactions and questions for your pharmacist. Banned or restricted herbs are covered in ephedra and other banned ingredients.Frequently asked questions
If an herb is not on this table, is it safe?
Not necessarily. Lack of evidence is not proof of safety, and this table only covers herbs we read sources for. Ask a pharmacist.
Which herb-medicine combinations are the most serious?
The sources we read stress serotonin effects with St. John's wort and certain antidepressants, and bleeding risk with blood thinners. [5][2] Yohimbe with MAOIs or tricyclic antidepressants should be avoided. [6]
Does a "natural" label mean no interaction?
No. MedlinePlus says many people believe natural products are always safe, and that this is not necessarily true. [22]
Who should I ask before starting an herb?
A pharmacist or clinician who knows your medicines and conditions. Bring the product label. See talking with a health professional.
What should I do before surgery?
Tell the surgical team about every herb and supplement. [1][3]
References
- NCCIH, Using Dietary Supplements Wisely (US NIH). Read 2026-10-23.
- NCCIH, Ginkgo (US NIH). Read 2026-10-23.
- NCCIH, Garlic (US NIH). Read 2026-10-23.
- NCCIH, Asian Ginseng (US NIH). Read 2026-10-23.
- NCCIH, St. John’s Wort (US NIH). Read 2026-10-23.
- NCCIH, Yohimbe (US NIH). Read 2026-10-23.
- NCCIH, Green Tea (US NIH). Read 2026-10-23.
- NCCIH, Goldenseal (US NIH). Read 2026-10-23.
- NCCIH, Kava (US NIH). Read 2026-10-23.
- NCCIH, Valerian (US NIH). Read 2026-10-23.
- NCCIH, Licorice Root (US NIH). Read 2026-10-23.
- NCCIH, Aloe Vera (US NIH). Read 2026-10-23.
- NCCIH, Ephedra: Usefulness and Safety (US NIH). Read 2026-10-23.
- LactMed (US NLM), Bitter Orange. Read 2026-10-23.
- NCCIH, Black Cohosh (US NIH). Read 2026-10-23.
- NCCIH, Turmeric (US NIH). Read 2026-10-23.
- Debelle FD et al., Aristolochic acid nephropathy: a worldwide problem. Kidney International 2008. Read 2026-10-23.
- NCCIH, Butterbur (US NIH). Read 2026-10-23.
- Authentication of Scutellaria lateriflora (skullcap) dietary supplements by flow-injection mass spectrometry. Analytical and Bioanalytical Chemistry 2011. Read 2026-10-23.
- NCCIH, Bitter Orange (US NIH). Read 2026-10-23.
- EMA/HMPC, Public statement on the use of herbal medicinal products containing toxic, unsaturated pyrrolizidine alkaloids (PAs), final, adopted 24 November 2014 (EMA/HMPC/893108/2011). Read 2026-10-23.
- MedlinePlus (US NLM), Herbal Medicine. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.