Integrative Therapeutics Vitamin C with Quercetin - Vitamin C Supplement for Immune Support*- Supports Antioxidant Activity* - Vegan, Gluten-Free & Dairy-Free - 180 Capsules (90 Servings)

Clinical trials typically use 500-1000mg daily. IT Vitamin C with Quercetin delivers Vitamin C with quercetin and bioflavonoids per 2-capsule serving (180 capsules, 90 servings), which we classify as Blend relative to that range.

See the "Also consider" section below for two alternatives. Choose based on form preference (Capsule vs alternatives), dose adequacy, and third-party testing.

Yes — GMP Certified. Third-party testing verifies ingredient identity and label accuracy.

Yes — Amazon Subscribe & Save is available for this product. Enrolling locks in a recurring delivery at a reduced per-unit price.

Quercetin may interact with certain antibiotics (fluoroquinolones), blood thinners (warfarin), and cyclosporine — consult your prescriber if you take these. High-dose vitamin C (above 1000mg) can increase the risk of kidney stones in susceptible individuals and may interfere with some lab tests. Citrus bioflavonoids have minimal known drug interactions.

Vitamin C at supplemental doses is water-soluble and generally safe long-term; excess is excreted in urine. Quercetin at high doses (above 1g/day) has been associated with headaches and tingling in some clinical studies. The doses in this formula are likely below the level that causes these effects.

High-dose vitamin C (above 1000mg) can cause loose stools or diarrhea — the buffered or combined format in this product may reduce that risk. Quercetin is generally well tolerated but can cause mild GI discomfort in sensitive individuals. Taking with food minimizes this.

Pairs well with zinc (complementary immune support) and vitamin D. Avoid stacking with other high-dose quercetin or vitamin C products to prevent excessive intake. Quercetin can chelate iron and zinc — separate from iron supplements by 2 hours if taking both.

Take 2 capsules daily with food, or as directed by a healthcare professional. Avoid taking large vitamin C doses before lab tests (can falsely elevate some markers). Pregnant or nursing women should consult their doctor before use, particularly regarding quercetin.

Antioxidant and immune support effects from vitamin C accumulate over 1–2 weeks of consistent daily use. Quercetin's anti-inflammatory and antioxidant activity builds within days to weeks of regular intake. For acute immune support at first sign of illness, some protocols use higher short-term doses.