Drug interactions
Calcium + Tetracycline
Severity: Moderate
Calcium and Tetracycline: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Oral calcium substantially lowers tetracycline absorption, risking inadequate antibiotic exposure and therapeutic failure. This applies to supplements, antacids and calcium-rich products taken at the same time.
What this interaction means in plain words
Calcium and Tetracycline can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Calcium belongs to Gastrointestinal Tract; Tetracycline belongs to Anti Bacterial.
Why it happens
Calcium cations chelate tetracycline in the gastrointestinal tract, creating insoluble complexes that are poorly absorbed.
What to do
Give tetracycline at least 2 hours before or 4 hours after calcium. Use a non-chelating antibiotic if separation is impractical.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Calcium
- Calcium + Ceftriaxone Contraindicated
- Acalabrutinib + Calcium Moderate
- Alendronate + Calcium Moderate
- Atazanavir + Calcium Moderate
- Baloxavir marboxil + Calcium Moderate
- Bendroflumethiazide + Calcium Moderate
Other interactions of Tetracycline
- Acitretin + Tetracycline Contraindicated
- Methoxyflurane + Tetracycline Contraindicated
- Isotretinoin + Tetracycline Major
- Palovarotene + Tetracycline Major
- Strontium ranelate + Tetracycline Major
- Tetracycline + Tretinoin Major
Frequently asked questions
Can I take Calcium with Tetracycline?
MediHelp rates the interaction as moderate. Calcium and Tetracycline can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Oral calcium substantially lowers tetracycline absorption, risking inadequate antibiotic exposure and therapeutic failure. This applies to supplements, antacids and calcium-rich products taken at the same time.
How serious is the interaction between Calcium and Tetracycline?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Give tetracycline at least 2 hours before or 4 hours after calcium. Use a non-chelating antibiotic if separation is impractical.
What other medicines interact with Calcium?
MediHelp also lists interactions of Calcium with, for example, Ceftriaxone, Acalabrutinib, Alendronate. The full list is on the Calcium page.
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