MajorMineral supplements. Calcium×Tetracyclines
Updated · Methodology
Mechanism
The doxycycline label states that tetracycline absorption is reduced by antacids or other drugs containing divalent or trivalent cations such as calcium, magnesium or iron, and advises spacing by 2 to 3 hours. Doxycycline is often prescribed in long courses for acne or rosacea, exactly when calcium is taken daily.
Symptoms
Acne or rosacea fails to improve after 6–8 weeks of correct treatment, and the dose gets raised when the problem is the timing.
Management
Space by 2–3 hours. Doxycycline is taken with plenty of water and without lying down afterwards because of oesophagitis risk, which fits a midday dose; calcium then goes with dinner.
Check the full regimen, not just this pair
Opens the checker with these two drugs prefilled. Add the rest of the regimen and recompute additive risks.
Summary of a multi-drug list →
Medicine list: everything you take in one place →
Sources
- AEMPS: Ficha técnica Doxiciclina Normon 100 mg comprimidos recubiertos (2024)– AEMPS, CIMA, nº registro 47077, sección 4.5
- NIH Office of Dietary Supplements: Calcium – Health Professional Fact Sheet (2025)– NIH ODS, Calcium, Interactions with Medications