NSTK · 01.2026Independent supplement reference
NutriStack
Edition 1.0Updated July 13, 2026

Cimetidine

Prescription ·Exploratory record · not publication-reviewed ·Updated July 13, 2026

The first commercially available H2 receptor antagonist, cimetidine is used for the treatment of duodenal and gastric ulcers, GERD, and pathological hypersecretory conditions. While effective, it has largely been supplanted by famotidine and PPIs due to its notable drug interaction profile via cytochrome P450 inhibition.

Evidence tier
Strong
Indexed sources
10 1981–2024
Interactions
0
Depletes
2 nutrients
Read the sources → Compare profiles
Publication status

Exploratory record, not a reviewed medical publication.

See the editorial and medical-review policies for the publication gate.

This generated database record has not completed a claim-level review by a qualified human medical reviewer. Bibliography links and evidence labels are not approval. The page remains available for reference and is excluded from search indexing.

In short

What the research says.

A quick, data-only summary. The full evidence, dosing, and sources are below.

The first commercially available H2 receptor antagonist, cimetidine is used for the treatment of duodenal and gastric ulcers, GERD, and pathological hypersecretory conditions. NutriStack rates the supporting evidence as strong. Common adult dosing is 200–800 mg two to four times daily (as prescribed by your physician), though a prescriber sets the actual dose. With long-term use it can deplete vitamin b12, iron. This profile indexes 10 sources.

What it's good for
  • Healing of duodenal and gastric ulcers5
  • Relief of GERD symptoms
  • Treatment of pathological hypersecretory conditions
  • Heartburn and acid indigestion relief
What to watch for
  • Headache
  • Dizziness
  • Diarrhea
  • Known hypersensitivity to cimetidine1,2
  • Caution with drugs metabolized by CYP450 (warfarin, theophylline, phenytoin)6

The bottom line

Evidence rating strong. Most-documented uses: healing of duodenal and gastric ulcers, relief of gerd symptoms, treatment of pathological hypersecretory conditions. 10 sources indexed (1981–2024), with 0 interaction records on file.

The science

How it works, mechanistically.

Core mechanism

Competitively inhibits histamine at H2 receptors on gastric parietal cells, reducing basal and stimulated gastric acid secretion. Cimetidine also has weak anti-androgenic activity and inhibits several hepatic cytochrome P450 enzymes (CYP1A2, CYP2C9, CYP2D6, CYP3A4), leading to significant drug interactions.

Class
H2 Receptor Antagonist
Absorption
Water-soluble; take with food
Dosing

Dosing & protocol.

Common range
200–800 mg two to four times daily (as prescribed by your physician)
Recommended form
Tablet or oral liquid

May be taken with meals and at bedtime; antacids may reduce absorption if taken simultaneously

Depletions

What it depletes.

Nutrients this medication can lower over time, and what to replace.

Vitamin B12

Mild

Chronic cimetidine therapy can reduce gastric acid and impair liberation of protein-bound vitamin B12 from food.

Replace MethylcobalaminMonitor Serum B12 + methylmalonic acidOnset Usually after months to years of continuous therapy

Iron

Mild

Acid suppression can reduce non-heme iron solubility and food iron absorption during chronic therapy.

Replace Iron BisglycinateMonitor Ferritin + transferrin saturationOnset Usually with chronic acid suppression or low iron intake

Full Cimetidine depletion and interaction guide →

Safety

Full safety detail.

Side effects

  • Headache
  • Dizziness
  • Diarrhea
  • Gynecomastia (with prolonged use at high doses)
  • Confusion (especially in elderly or renally impaired)
  • Impotence (rare, dose-related)
  • Drug interactions via CYP450 inhibition

Contraindications

  • Known hypersensitivity to cimetidine1,2
  • Caution with drugs metabolized by CYP450 (warfarin, theophylline, phenytoin)6
  • Severe renal or hepatic impairment (dose adjustment required)
  • Caution in elderly patients (increased risk of CNS effects)
Sources

Sources, by evidence tier.

Numbered references. Citations throughout the page link here.

Meta-analyses & systematic reviews

2

Randomized controlled trials

3

Reference material

5
FAQ

Common questions.

Quick answers about Cimetidine, drawn from the data on this page.

What is Cimetidine?

The first commercially available H2 receptor antagonist, cimetidine is used for the treatment of duodenal and gastric ulcers, GERD, and pathological hypersecretory conditions. While effective, it has largely been supplanted by famotidine and PPIs due to its notable drug interaction profile via cytochrome P450 inhibition.

What is Cimetidine used for?

Commonly cited benefits of Cimetidine include: Healing of duodenal and gastric ulcers; Relief of GERD symptoms; Treatment of pathological hypersecretory conditions; Heartburn and acid indigestion relief. NutriStack rates the overall evidence as strong.

What is a typical dose of Cimetidine?

A typical adult dose of Cimetidine is 200–800 mg two to four times daily (as prescribed by your physician). The commonly recommended form is Tablet or oral liquid. These are general ranges, not personalized advice; confirm the right dose with a clinician.

What are the side effects of Cimetidine?

Reported side effects include headache, dizziness, diarrhea, gynecomastia (with prolonged use at high doses), confusion (especially in elderly or renally impaired), impotence (rare, dose-related). This is educational information; check with a healthcare professional before use.

How strong is the evidence for Cimetidine?

NutriStack rates this as Strong, meaning multiple high-quality meta-analyses or systematic reviews converge on the same finding. Full tier criteria are at https://nutristackapp.com/methodology/evidence-tiers.

Use this with your stack

Cimetidine in NutriStack.

Add it to your stack, see how it interacts with everything else you take, and get a Stack Score that updates the moment it does.

Download on the App Store → Read the methodology

NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.