An Important Note on Medication Interactions
Quercetin is a plant bioflavonoid studied for antioxidant activity, alongside vitamin C, which has an established, EU-authorised role in normal immune function and reducing tiredness and fatigue. The 500mg dose in this product falls within the range used in clinical trials (up to 500mg twice daily for 12 weeks) without serious adverse events reported.
The most important thing to know about quercetin, more than for most supplements in this category: it genuinely inhibits several liver enzymes (CYP3A4, CYP2D6, CYP2C19, and CYP1A2) involved in metabolising a wide range of common medications. This isn’t a theoretical concern — there’s a documented clinical case of a patient on stable warfarin therapy experiencing a significantly elevated INR (a measure of blood clotting time) after starting quercetin, which normalised after stopping it. Medications affected by these same enzyme pathways include certain antidepressants (such as paroxetine and venlafaxine), some heart and blood pressure medications (including flecainide and metoprolol), tamoxifen, and quinolone antibiotics, among others — if you take any regular prescription medication, it’s genuinely worth checking with your GP or pharmacist before starting quercetin, rather than assuming it’s automatically compatible because it’s a “natural” antioxidant.
Cyclosporine specifically should not be combined with quercetin without direct medical supervision, given a well-documented interaction risk. If you have kidney problems, quercetin is worth discussing with your GP first, and safety data during pregnancy and breastfeeding is limited, so it’s best avoided in these situations without medical guidance.
Sourced from Sophora japonica flowers, this formula is vegan, free from unnecessary fillers or preservatives, and manufactured in the UK with batch testing for potency and purity. Take one capsule daily with water during a meal, which also helps reduce the mild digestive upset (nausea, headache) some people experience when starting. 180 capsules provide a 6-month supply.
