Is Calcium (antacids/supplements) Safe with doxycycline?
Free · No account · based on published sources including NIH ODS, FDA drug labels, and peer-reviewed literature
Avoid taking calcium-containing antacids or supplements at the same time as doxycycline. Separate doses by at least 2-3 hours.
Why this interaction occurs
The FDA label states that absorption of tetracyclines is impaired by antacids containing calcium, which can result in lower doxycycline concentrations and reduced antibiotic effectiveness.
Evidence
Evidence level: strong.
Data source
FDA Drug Label
Reported safety data
The FDA’s adverse event reporting system (FAERS) has received 72,559 reports mentioning doxycycline. This reflects reported cases involving the medication in general — not confirmed causation, and not specific to the doxycycline + supplement combination on this page.
FAERS reports are voluntary and cannot prove that a drug caused an event. Do not use report counts to assess the safety of this specific drug-supplement pair.
Frequently asked questions
Related interactions
All Calcium (antacids/supplements) interactions → · All doxycycline interactions →
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Educational only — not medical advice.
Always confirm with your doctor or pharmacist.