NutriStack
Pick two, see the receipt.
1,730 fully-cited supplement and prescription interaction pairs across 389 substances. Every claim links to its primary source. No login, no paywall, no proprietary score.
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Check a pair
Choose two substances.
Interaction checker
Database shape
What is in the index.
Counts
- Pairs
- 1,730
- Substances
- 389
- Citation rows
- 1,745
- Prescription pairs
- 1,029
- Supplement-only pairs
- 701
Verdict distribution
Distribution by primary verdict. Most pairings are synergies; conflicts and contraindications are rare and explicitly flagged.
Featured pairs
Twelve to start with.
The most-asked pairs across coaching threads, supplement subreddits, and prescription patient handouts.
Notable pairings
| Verdict | Pair | One-liner | Evidence |
|---|---|---|---|
| Synergy | Iron + Vitamin C | Vitamin C dramatically increases non-heme iron absorption by reducing ferric iron (Fe3+) to ferrous iron (Fe2+) and forming a soluble... | Strong |
| Conflict | Calcium + Iron | Calcium significantly inhibits both heme and non-heme iron absorption when taken simultaneously. | Strong |
| Synergy | Vitamin D3 + Vitamin K2 | Vitamin D3 increases calcium absorption, while K2 activates osteocalcin and matrix GLA protein to direct calcium into bones and away from... | Moderate |
| Contraindicated | 5-HTP + L-Tryptophan | Both 5-HTP and L-Tryptophan increase serotonin synthesis. Combining them creates additive serotonin excess, risking serotonin syndrome. | Moderate |
| Synergy | Atorvastatin + Coenzyme Q10 Ubiquinol | Atorvastatin inhibits HMG-CoA reductase, which also reduces endogenous CoQ10 synthesis. Statin-induced CoQ10 depletion may contribute to... | Moderate |
| Timing Sensitive | Calcium + Levothyroxine | Calcium supplements significantly reduce levothyroxine absorption by 20-25% through chelation in the gastrointestinal tract. This can lead... | Strong |
| Contraindicated | St. John's Wort + Warfarin | St. John's Wort is a potent inducer of CYP3A4, CYP2C9, and P-glycoprotein, which dramatically accelerates warfarin metabolism and reduces... | Strong |
| Synergy | L-Theanine + Magnesium Glycinate | L-theanine and magnesium are both studied for relaxation-related markers, but direct combination evidence is limited. | Emerging |
| Caution | Copper + Zinc | Chronic high-dose zinc supplementation (>40mg/day) can induce copper deficiency by upregulating metallothionein, which binds copper in... | Strong |
| Conflict | Iron + Zinc | Iron and zinc compete for the same absorption pathways when taken together in supplement form. | Strong |
| Synergy | Magnesium Glycinate + Vitamin D3 | Magnesium is essential for vitamin D metabolism. It's required for the enzymes that convert D3 to its active form calcitriol. | Strong |
| Synergy | Coenzyme Q10 + Fish Oil | CoQ10 is fat-soluble and absorption increases 3-fold when taken with dietary fat. Fish oil provides the ideal fat vehicle. | Strong |
Most-paired substances
Browse by substance.
The 20 substances with the most interaction coverage. Tap a name for its full research profile.
Top 20
| Substance | Pairings in the database |
|---|---|
| St. John's Wort | 68 pairs |
| Alcohol | 65 pairs |
| Fish Oil | 59 pairs |
| Iron | 57 pairs |
| Magnesium Glycinate | 55 pairs |
| Vitamin D3 | 54 pairs |
| Calcium | 53 pairs |
| Vitamin C | 49 pairs |
| Potassium | 48 pairs |
| Zinc | 43 pairs |
| Melatonin | 39 pairs |
| Coenzyme Q10 | 39 pairs |
| Berberine | 39 pairs |
| Warfarin | 36 pairs |
| Turmeric/Curcumin | 35 pairs |
| Ginkgo Biloba | 35 pairs |
| Garlic Extract | 34 pairs |
| 5-HTP | 32 pairs |
| Alpha-Lipoic Acid | 31 pairs |
| Probiotics | 29 pairs |
Methodology
Every claim links to its primary source.
Each row includes 1–6 sources with PMIDs where available. Acceptance criteria, evidence tiers, and the public downgrade policy are documented at /methodology/interactions and /methodology/evidence-tiers.