Can You Take St. John's Wort with Fish Oil?
Yes, you can take St. John's wort with fish oil—there is no direct pharmacological interaction between these two supplements, and they work through entirely different mechanisms. However, there are important safety considerations you need to understand before combining them.
Key Safety Considerations
St. John's Wort Drug Interactions (Critical)
While St. John's wort doesn't interact with fish oil itself, St. John's wort is a potent inducer of CYP3A4 and P-glycoprotein enzymes 1. This means it can significantly reduce blood levels of many prescription medications, including:
- Anticoagulants (warfarin, NOACs like dabigatran, rivaroxaban, apixaban, edoxaban) - St. John's wort decreases their effectiveness, increasing clot risk 1
- Antidepressants (risk of serotonin syndrome or reduced efficacy)
- Oral contraceptives
- Immunosuppressants
- Many cancer chemotherapy agents
The concomitant use of St. John's wort with NOACs is not recommended due to relevant decreases in anticoagulant levels 1.
Fish Oil Considerations
Fish oil is generally safe at typical supplemental doses:
- Up to 5 g/day combined EPA and DHA does not raise safety concerns for adults 2
- Mild gastrointestinal effects (fishy aftertaste, belching) are the most common side effects 2
Important exception: If you're taking ibrutinib (for chronic lymphocytic leukemia), avoid fish oil supplements entirely due to increased bleeding risk (epistaxis) 2.
Bleeding Risk Assessment
The combination does NOT create additive bleeding risk from a pharmacological standpoint. However:
- Fish oil alone: The European Food Safety Authority concluded that fish oil up to 5 g/day does not increase spontaneous bleeding risk 2
- St. John's wort: No inherent bleeding risk, but it's photosensitizing 3
- If you're on antiplatelet drugs (aspirin, clopidogrel) or anticoagulants, consult your physician before adding either supplement
Practical Recommendations
You Can Safely Combine Them If:
- You are NOT taking prescription medications (especially anticoagulants, antidepressants, or chemotherapy)
- You are NOT taking ibrutinib
- You are NOT undergoing phototherapy
- You are NOT pregnant or breastfeeding (safety unknown for both) 3
Dosing Guidelines:
- Fish oil: 1-2 g/day EPA+DHA for general cardiovascular health 4; up to 2-4 g/day for hypertriglyceridemia 4
- St. John's wort: Typical doses range from 300-1800 mg/day of standardized extract 5
Monitor For:
With fish oil 6:
- Fasting blood sugar
- LDL cholesterol
- Liver enzymes (GPT)
- Hemoglobin/hematocrit (if on higher doses)
With St. John's wort 3:
- Photosensitivity (avoid excessive sun exposure, especially if on phototherapy)
- Any signs your prescription medications are becoming less effective
Clinical Context
Both supplements have been studied for depression treatment. St. John's wort has the strongest evidence for mild-to-moderate depression 5, 7, 8, while fish oil (particularly EPA-predominant formulations) shows benefits in some depression studies 6, 9, 8. However, both carry risk of inducing mania in bipolar disorder 7.
Bottom Line
The combination is pharmacologically safe, but St. John's wort's drug interactions are the primary concern—not its interaction with fish oil. If you're on any prescription medications, you must discuss St. John's wort with your physician first. Fish oil is generally well-tolerated and can be used safely at recommended doses in most people.