Supplement Interaction Checker
Check for interactions between supplements, vitamins, and common medications. Our database covers synergies, cautions, and conflicts to help you supplement safely.
Complete Interaction Database
Browse our full database of supplement and medication interactions. Each entry includes the type of interaction (synergy, caution, or conflict), a detailed description, and practical recommendations.
Vitamin K2 directs calcium (absorbed via D3) to bones and away from arteries. These two work together to optimize calcium metabolism.
Magnesium is required for the enzymatic conversion of vitamin D into its active form (calcitriol). Without adequate magnesium, vitamin D supplementation may be less effective.
Calcium significantly inhibits iron absorption when taken at the same time. Studies show calcium can reduce iron absorption by 50–60%.
Vitamin C dramatically enhances non-heme iron absorption by converting ferric iron to the more absorbable ferrous form. Can increase absorption by 2–6 times.
Iron and zinc compete for the same absorption pathways (DMT1 transporter). Taking them together reduces absorption of both minerals.
Long-term zinc supplementation (>40 mg/day) can deplete copper levels by inducing metallothionein, which binds copper in the gut and prevents absorption.
High doses of calcium can interfere with magnesium absorption and vice versa. They compete for absorption in the intestine.
Vitamin E protects omega-3 fatty acids from oxidation (lipid peroxidation). Fish oil supplementation may increase vitamin E requirements.
Ashwagandha can increase thyroid hormone levels (T3 and T4). This may cause hyperthyroid symptoms in people already on thyroid medication.
Combining St. John's Wort with SSRIs can cause serotonin syndrome, a potentially life-threatening condition caused by excessive serotonin activity.
Vitamin K directly counteracts warfarin's mechanism of action (warfarin works by inhibiting vitamin K-dependent clotting factors). Even small amounts can destabilize INR.
Statins inhibit the mevalonate pathway, which produces both cholesterol and CoQ10. Statin use can deplete CoQ10 levels by 40%, contributing to muscle pain and fatigue.
Early research suggested caffeine might blunt creatine's benefits, but more recent and rigorous studies show no significant negative interaction. They can be used together.
Antibiotics kill beneficial bacteria along with pathogens. Taking probiotics during antibiotic treatment can help maintain gut flora, but timing matters.
Piperine (from black pepper) increases curcumin bioavailability by 2,000% by inhibiting glucuronidation in the gut and liver.
Magnesium supports melatonin production and GABA receptor function. Together, they create a complementary sleep support stack.
Activated charcoal binds to NAC and many other supplements in the gut, preventing absorption. This applies to most oral supplements.
Both berberine and metformin lower blood sugar through similar mechanisms (AMPK activation). Combining them may cause hypoglycemia.
L-theanine smooths out caffeine's stimulant effects, reducing jitteriness and anxiety while preserving alertness and focus. This is one of the most well-studied nootropic combinations.
B12 and folate work together in the methylation cycle. Supplementing one without the other can mask deficiency symptoms of the other.
Fish oil has mild anticoagulant effects. At high doses (>3g EPA+DHA/day), it may increase bleeding risk when combined with blood thinners like warfarin or aspirin.
Grapefruit inhibits CYP3A4 enzymes in the gut and liver, dramatically altering the metabolism of many medications including statins, calcium channel blockers, and immunosuppressants.
Important: This tool is for educational purposes only and does not replace professional medical advice. Our interaction database covers common supplement-supplement and supplement-drug interactions but is not exhaustive. Always consult with a pharmacist or physician before combining supplements with prescription medications.