Common Supplement Interactions

Browse 20 researched interaction pairs. Click any to learn more about severity, mechanism, and timing.

Vitamin D3 + Calcium
SynergisticSafe

Vitamin D3 enhances calcium absorption. These are commonly taken together and considered a beneficial pairing.

Iron + Vitamin C
SynergisticSafe

Vitamin C significantly enhances non-heme iron absorption. Take together for maximum benefit.

Calcium + Iron
AbsorptionModerate

Calcium can significantly reduce iron absorption. Take these supplements at least 2 hours apart.

St. John's Wort + 5-HTP
AntagonisticSevere

Both increase serotonin levels. Combined use may lead to serotonin syndrome. Do not combine without medical supervision.

Zinc + Copper
AbsorptionModerate

High-dose zinc supplementation can deplete copper levels over time. If taking zinc long-term, consider a zinc:copper ratio of 15:1.

Magnesium + Calcium
AbsorptionMild

High doses of calcium can reduce magnesium absorption. Best to take at different times of day for optimal absorption.

Vitamin K2 + Vitamin D3
SynergisticSafe

K2 and D3 work synergistically for bone health. D3 increases calcium absorption while K2 directs it to bones.

Fish Oil (Omega-3) + Vitamin E
SynergisticSafe

Vitamin E helps prevent oxidation of omega-3 fatty acids. Many fish oil supplements already include vitamin E.

Turmeric (Curcumin) + Black Pepper (Piperine)
SynergisticSafe

Piperine increases curcumin absorption by up to 2000%. These are commonly combined for maximum effectiveness.

Vitamin B12 + Folate
SynergisticSafe

B12 and folate work together in methylation processes. Supplementing one without the other can mask deficiency symptoms.

Calcium + Zinc
AbsorptionMild

High doses of calcium may reduce zinc absorption. Space these apart by at least 2 hours.

Iron + Green Tea (EGCG)
AbsorptionModerate

EGCG in green tea can inhibit non-heme iron absorption. Avoid taking iron supplements with green tea.

Vitamin D3 + Magnesium
SynergisticSafe

Magnesium is required for vitamin D metabolism. Adequate magnesium helps activate vitamin D in the body.

Melatonin + Magnesium
SynergisticSafe

Both support sleep quality through complementary mechanisms. Magnesium promotes muscle relaxation while melatonin regulates circadian rhythm.

Ashwagandha + Rhodiola Rosea
SynergisticMild

Both are adaptogenic herbs that help manage stress. They can be combined but start with lower doses as effects may be additive.

Probiotics + Prebiotics
SynergisticSafe

Prebiotics serve as food for probiotic bacteria. This combination (synbiotics) enhances probiotic effectiveness.

CoQ10 + Fish Oil
SynergisticSafe

CoQ10 is fat-soluble and absorbs better with omega-3 fats. Both support cardiovascular health.

Calcium + Magnesium
TimingMild

Take calcium and magnesium at different times for better absorption. Both compete for the same transport pathways.

Vitamin C + Vitamin B12
AbsorptionMild

High doses of vitamin C may reduce B12 absorption. Space apart or take B12 in the morning and vitamin C later.

L-Theanine + Caffeine
SynergisticSafe

L-Theanine smooths out caffeine's stimulating effects, reducing jitters while maintaining focus. A classic nootropic pairing.

Want to check a specific combination?

Use AI Interaction Checker