Supplements and Ethinylestradiol with desogestrel.
Ethinylestradiol with desogestrel, sold under the brand names Marvelon, Mercilon, Gedarel, is a combined oral contraceptive: it provides oestrogen and progestogen for ovulation suppression and cycle control.
Ethinylestradiol with desogestrel is a combined oral contraceptive, providing oestrogen and progestogen for ovulation suppression and cycle control. The class is metabolised by CYP3A4 in the liver. That is where the supplement surface sits. St John's Wort induces CYP3A4 strongly enough to reduce contraceptive efficacy. The BNF and MHRA both flag this, and the Faculty of Sexual and Reproductive Healthcare advises against the combination. Several other strong CYP3A4 inducers (rifampicin, certain antiepileptics) carry the same concern. Among supplements at standard doses the signal is much smaller, but at high doses some 3A4-active compounds may have a marginal effect. The other clinically important issue is the venous thromboembolism risk profile. Third-generation progestogens carry a slightly higher VTE signal than second-generation. Any supplement decision in a patient at high VTE risk (smoker, obesity, family history) should account for the baseline.
Below are the 2 documented pairs we have explicitly assessed against Ethinylestradiol with desogestrel in the Distil database: 1 red and 1 amber. The pairs cluster around 2 mechanisms: CYP3A4 induction and Hormonal axis modulation. Every call is cited to either a clinical reference (PMID) or the British National Formulary. Anything not on this list is either still to be assessed or beyond our database scope. The checker beneath surfaces assessments by supplement, and the missing-item form at the bottom of the page routes any uncatalogued supplement into our next curation pass.
Documented interactions
Last reviewed 17 June 2026. Each interaction below lists the evidence its assessment drew on: some rest on studies of the exact pair, others on mechanism evidence, where a citation may support one part of the reasoning rather than the exact combination. The evidence line on each entry says which.
CYP3A4 induction
Red Does St John's Wort interact with ?
St John's Wort can reduce the contraceptive reliability of the combined pill. Breakthrough bleeding is the warning sign, and unintended pregnancies have been reported on this combination. We treat this as a do-not-combine pair.
Evidence: Supported by human study data.
Hormonal axis modulation
Amber Does Vitex interact with ?
Vitex (chasteberry) acts on the body's hormone signals: it lowers prolactin and, in lab studies, gently nudges oestrogen and progesterone receptors. The combined pill works by holding your hormones at set levels, so in theory vitex could work against that balance, and the pill's hormones could equally blunt what vitex is meant to do. There is no study showing the pill actually fails when vitex is added, so this is a caution rather than a firm warning. If you take the combined pill, mention vitex to your prescriber before adding it, and treat any breakthrough bleeding as a reason to check in.
Evidence: Based on an established mechanism, with no direct study of this exact combination yet.
Reviewer-flagged: awaiting clinical-reviewer sign-off.
What this list does not say. Pairs not flagged here are not implicitly safe. They are either not yet in our database, or fall outside our inclusion scope (food-supplement interactions only; for drug-drug interactions, the BNF is authoritative). Use the checker below to surface any supplement, and submit a missing item if you take something we have not catalogued.
No affiliates. No commission. We earn nothing on what you buy.
How we grade severity, choose what's in scope, and what we exclude.
Every call on this page is reasoned. We publish the full rubric for severity tiers, the medication inclusion logic, the evidence grades we accept, and what we deliberately leave out. About three thousand words. Worth reading once if you use this tool more than occasionally.
Read the full methodologyA full supplement review, built around you, not a generic stack.
The free checker answers one interaction question at a time. A Distil report reviews the bigger picture: your goals, diet, medications, current supplements and any blood results you provide, then shows what appears worth keeping, changing, adding or leaving out.
- what your diet already covers, so you are not adding a capsule for something food is already handling
- which evidence-graded compounds are worth considering for your goals, and which were considered but left out
- what to keep, change or stop from what you already take, plus the order to introduce anything new
- how your medications and complete supplement stack fit together, with daily timing and a clear point for reassessment
The interaction check is one section of the full report. You also get the reasoning behind each recommendation and the evidence references used.
£49 introductory price for early customers. Standard price £79.
Something missing?
If a supplement or medication you take isn't in our autocomplete, tell us. We go through what people flag every week and add what's missing.