What Supplements Should I Avoid on Antidepressants?

Several common supplements can interact meaningfully with antidepressants. NPS MedicineWise and TGA guidance describe St John’s Wort, 5-HTP, and some other supplements as carrying significant interaction risk with SSRIs and SNRIs. The general rule: check with your pharmacist or prescriber before adding any supplement.

Supplements with known significant interactions

St John’s Wort — commonly used for mood but shares a mechanism with SSRIs; combining them can produce serotonin syndrome (a serious, sometimes life-threatening reaction). 5-HTP and tryptophan — precursors to serotonin; carry similar risk. SAMe — similar caution. These are the most commonly cited interactions in TGA and NPS MedicineWise guidance.

Supplements with moderate interaction risk

High-dose omega-3 (fish oil) is generally safe and sometimes recommended alongside antidepressants, but discuss dose with your prescriber. Ginkgo biloba can affect bleeding risk when combined with SSRIs. Kava can affect liver metabolism of some antidepressants. Ginseng has variable effects on some psychiatric medications. The same check-first habit applies to over-the-counter painkillers, which carry their own interactions.

Generally low-risk supplements

Standard multivitamins are usually fine. Vitamin D, B12, and standard iron supplements typically do not interact. However — the safest approach for any supplement is a quick check with your pharmacist or prescriber, particularly if you are taking it regularly rather than occasionally. Everyday substances like caffeine can also behave differently on an antidepressant, so it is worth knowing your own response.

What to flag to your prescriber

Raise these at any review

Any new supplement you are considering starting.
Symptoms of serotonin syndrome — high fever, sweating, confusion, muscle twitching, racing heart.
Unusual bleeding while combining supplements with your antidepressant.
Any supplement marketed for mood, sleep, or anxiety.

Frequently asked questions

Can I take St John’s Wort with my antidepressant?

No. St John’s Wort combined with SSRIs or SNRIs risks serotonin syndrome, which can be serious.

Is fish oil safe with antidepressants?

Standard-dose fish oil is generally considered safe. High-dose omega-3 for its own antidepressant effect should be discussed with your prescriber.

Are vitamins safe to take with antidepressants?

Standard multivitamins are usually safe. Check with your pharmacist for anything specific, particularly high doses.

Evidence and sources referenced

NICE Guideline NG222 — Depression in adults: treatment and management (United Kingdom).
Royal Australian and New Zealand College of Psychiatrists (RANZCP) — Clinical Practice Guidelines for Mood Disorders.
NPS MedicineWise — prescriber and patient resources on antidepressant treatment (Australia).
Royal College of Psychiatrists — patient information on antidepressants.
TGA and FDA — product information for SSRI and SNRI medication classes.
Maudsley Prescribing Guidelines in Psychiatry — prescribing patterns and side-effect timelines.