A complete safety, timing, and dosage guide for combining St. John's Wort with Vitamin B2 (Riboflavin) — including how the two supplements interact, the best time of day to take each, and which populations should be careful.
Yes, you can safely take Vitamin B2 (Riboflavin) and St. John's Wort together. No known interaction exists between these two supplements, so combining them is generally considered low-risk.
Vitamin B2 (Riboflavin) and St. John's Wort together have a neutral interaction profile. St. John's Wort does not affect the way your body absorbs or uses riboflavin, and riboflavin does not alter St. John's Wort's usual metabolic pathways. For most healthy adults, taking both is safe, though remember that St. John's Wort can interact with many prescription medications.
Riboflavin is a water-soluble B vitamin absorbed in the upper small intestine via specific carrier proteins (RFVT1–3), then converted inside cells to flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), which function as coenzymes in energy production and antioxidant systems. St. John's Wort, on the other hand, exerts its effects by inhibiting the reuptake of serotonin and other neurotransmitters, and it also acts as a potent inducer of cytochrome P450 enzymes (especially CYP3A4) and P-glycoprotein efflux pumps. Riboflavin is neither a substrate nor an inhibitor of these enzymes or transporters, and it does not share any common absorption, distribution, or metabolic pathway with the active compounds in St. John's Wort. Therefore, the two supplements work in different physiological systems without directly influencing each other's levels or activity.
If you need both a riboflavin supplement and St. John's Wort, take them together with a meal that contains some protein and healthy fat to help your body absorb riboflavin more efficiently. There is no need to separate them by hours, since they do not compete for absorption or metabolism. A single daily dose of riboflavin (typically 10–25 mg) is enough for most adults, and St. John's Wort is usually taken 2–3 times daily with food. If you miss a dose of riboflavin, just take it with your next meal; if you miss a dose of St. John's Wort, skip it and resume your regular schedule—do not double the dose. Always keep your pharmacist informed about every supplement you take, especially because St. John's Wort interacts with so many medications.
Riboflavin is commonly available as plain riboflavin or as riboflavin-5'-phosphate (sometimes labeled as FMN), both of which are well absorbed and behave similarly in the body. St. John's Wort products vary in their content of hypericin and hyperforin, but this variability does not change the lack of interaction with riboflavin. No specific form of either supplement creates a meaningful interaction risk.
Riboflavin is commonly included in B-complex formulas and in migraine-support stacks alongside magnesium and coenzyme Q10. St. John's Wort is usually taken alone or in mood-support blends that include other herbs such as passionflower or lemon balm, but it is not traditionally paired with riboflavin in a single formulation.
Yes, you can take Vitamin B2 (Riboflavin) and St. John's Wort at the same time. I have not seen any evidence that St. John's Wort changes how riboflavin works or that riboflavin changes how St. John's Wort works. Taking them together with food is completely fine for most people.
Yes, it is safe to combine Vitamin B2 (Riboflavin) with St. John's Wort every day. Riboflavin is a water-soluble vitamin you need regularly, and St. John's Wort's impact on liver enzymes does not affect riboflavin levels. I would still recommend checking with your doctor, especially because St. John's Wort interacts with many prescription drugs.
You do not need to wait at all between them. I would simply take them together with a meal, because there is no absorption competition or metabolic conflict.
No, they do not compete for absorption. Riboflavin uses its own specific transporters in the gut, while St. John's Wort compounds are absorbed differently. They have separate pathways, so taking them together won't reduce each other's availability.
Most people can take this combination safely. However, I would advise avoiding St. John's Wort if you are pregnant, breastfeeding, or taking medications such as blood thinners, antidepressants, birth control pills, or immunosuppressants—not because of riboflavin, but because St. John's Wort itself can cause serious drug interactions. Riboflavin alone is safe for nearly everyone.
I recommend taking both with food. Riboflavin is absorbed better when taken with a meal, and St. John's Wort is less likely to cause stomach upset if administered with food. Taking them together at a meal is the simplest and most comfortable way.
Reviewed by Caroline M. on April 8, 2026 for accuracy against the sources listed above. This page is educational and is not a substitute for professional medical advice.
The matrix has 86 supplements and 7310 pairwise interactions. Click any cell to see the full breakdown.