Calcium

Which medicines interact with calcium?

Updated 4 Nov 2026

Short answer

The main ones are these, according to NIH:

  • Levothyroxine (thyroid hormone). Calcium carbonate can lower its absorption. The label says to keep the two 4 hours apart.[1]
  • Quinolone antibiotics, such as ciprofloxacin. Calcium lowers their absorption. Taking the antibiotic 2 hours before or 2 hours after calcium prevents this.[1]
  • Dolutegravir (HIV medicine). Calcium can lower its blood level a lot. The label says to take it 2 hours before or 6 hours after calcium.[1]
  • Lithium. Long-term use can cause high blood calcium, and calcium supplements could add to this risk.[1]

Some medicines, such as bisphosphonates, cisplatin and proton pump inhibitors, can lower blood calcium.[1]

Calcium also affects iron. In a review of human studies, more calcium lowered short-term iron absorption by about 5.6%. Ferritin, a marker of iron stores, was lower at higher calcium intakes, but hemoglobin did not fall.[2] People who take a medicine every day should ask a doctor or pharmacist about calcium.[1]

Sources (2)

  1. Calcium: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  2. Calcium Intake and Iron Status in Human Studies: A Systematic Review and Dose-Response Meta-Analysis of Randomized Trials and Crossover Studies. Abioye AI, Okuneye TA, Odesanya AO, Adisa O, Abioye AI, Soipe AI, et al. J Nutr, 2021. PMID 33758936

More about calcium

What is calcium?Which foods contain calcium?Does calcium need vitamin D to work?How much calcium can the body absorb at one time?What is calcium used for?What happens if you do not get enough calcium?

For education; not medical advice. Talk to a doctor before you start, stop or change a supplement.