Medication·Interactions & depletion·Reviewed June 9, 2026
Cimetidine interactions.
Cimetidine has 5 documented interactions in the NutriStack database. Prolonged use is also associated with lower Vitamin B12 and Iron. The full interaction list, depletion table, and replacement suggestions are below. None of this is a substitute for your prescriber's advice.
Cimetidine at a glance.
A quick, data-grounded summary. The full tables are below.
Cimetidine has 5 documented interactions in the NutriStack database. Prolonged use is also associated with lower Vitamin B12 and Iron. The full interaction list, depletion table, and replacement suggestions are below. None of this is a substitute for your prescriber's advice.
Substances that interact with cimetidine.
Every supplement and medication in the NutriStack database with a documented interaction with this drug, highest-severity first. Open any pair for the mechanism and sources.
| Substance | Interaction | What happens |
|---|---|---|
| Green Tea Extract | Caution | Cimetidine inhibits CYP1A2, the main enzyme that clears caffeine. Caffeine-containing green tea extract taken with cimetidine can produce higher and... details → |
| Iron | Caution | Cimetidine reduces gastric acid and modestly impairs absorption of oral iron salts, particularly ferrous sulfate. The H2 blocker class is associated... details → |
| Melatonin | Caution | Cimetidine is a potent inhibitor of CYP1A2, the main enzyme that clears melatonin. Co-administration can substantially raise melatonin plasma levels... details → |
| Vitamin B12 | Caution | Cimetidine reduces gastric acid and pepsin secretion enough to impair the release of dietary B12 from food protein. The Kaiser study linked two or... details → |
| Methylcobalamin | Synergy | Methylcobalamin (a free coenzyme form of B12) does not need gastric acid or pepsin to be released from food protein, making it a more reliable B12... details → |
What cimetidine can deplete.
Nutrients this medication is associated with lowering over time, with the mechanism, a suggested replacement where one applies, and the biomarker to monitor. Discuss any replacement with your prescriber first.
| Nutrient | Severity | How it happens | Replace with | Monitor |
|---|---|---|---|---|
| Vitamin B12 | Mild | Chronic cimetidine therapy can reduce gastric acid and impair liberation of protein-bound vitamin B12 from food. | Methylcobalamin | Serum B12 + methylmalonic acid |
| Iron | Mild | Acid suppression can reduce non-heme iron solubility and food iron absorption during chronic therapy. | Iron Bisglycinate | Ferritin + transferrin saturation |
The full cimetidine profile.
Uses, typical dosing, side effects, and the cited evidence for this medication.
Common cimetidine questions.
Quick answers drawn from the tables above.
What interacts with Cimetidine?
In the NutriStack database, Cimetidine has 5 documented interactions. The most notable include Green Tea Extract, Iron, Melatonin, Vitamin B12, and Methylcobalamin. Check any specific combination before taking it and confirm with your prescriber.
Does Cimetidine deplete any nutrients?
Cimetidine is associated with lowering Vitamin B12 and Iron with prolonged use. Useful biomarkers to monitor include Serum B12 + methylmalonic acid and Ferritin + transferrin saturation. Ask your prescriber before adding any replacement supplement.
Is it safe to take Green Tea Extract with Cimetidine?
NutriStack classifies the Green Tea Extract and Cimetidine pairing as caution: Cimetidine inhibits CYP1A2, the main enzyme that clears caffeine. Caffeine-containing green tea extract taken with cimetidine can produce higher and longer-lasting... If you take cimetidine, prefer a decaffeinated green tea extract or limit total caffeine intake. Watch for signs of caffeine excess like racing... Always confirm with your prescriber.
Check your whole stack
See how cimetidine fits your supplements.
NutriStack screens your full routine for interactions and depletions, and updates the moment you change it.