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Tetracycline is known to be inhibited by calcium ions, and milk contains quite some calcium ions. What I want to ask is, to what extent does drinking milk affect the effectiveness of orally taken tetracycline?

  • @user19679 yes I figured it was a chelator, so binding tendency should be very strong. However what I want to know is how much milk actually affects tetracycline effectiveness, also considering in vivo conditions. – busukxuan Jan 17 '16 at 10:28
  • What dose have you been prescribed? – user19679 Jan 17 '16 at 11:19
  • Hello and welcome to Health.SE! Personal medical advice is off-topic here, so I have removed the part of, our question that could be constructed as asking for it. In my opinion, your question can stand alone without it. – YviDe Jan 17 '16 at 12:25
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    @user19679 you have been told before not to answer in comments, so why do you continue to do so instead of writing an answer? This is clearly an answer with medical advice that needs references and a way for the community to downvote it of it's wrong. Please convert it to an answer instead of continuing to give medical advice like this. – YviDe Jan 17 '16 at 13:28
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    @user19679 and if you have a problem with that policy, feel free to discuss it on Meta instead of in the comments: meta.health.stackexchange.com/questions/378/… – YviDe Jan 17 '16 at 13:35
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Calcium-rich food interferes with absorption of tetracycline considerably:

Milk and other dairy products, antacids containing polyvalent cations, as well as various iron salts ingested simultaneously with tetracycline derivatives, might interfere with their absorption by 50 to 90% or even more.

Interactions with the Absorption of Tetracyclines

However, you can't calculate with that, by for example just taking twice the dosage. The safe method is to not ingest milk or any other calcium-rich food together with the tetracycline. The recommendation appears to be to leave one to two hours between the antibiotics and milk (taking the antibiotics first) :

Do not take milk, milk formulas, or other dairy products within 1 to 2 hours of the time you take tetracyclines (except doxycycline and minocycline) by mouth

The study referenced above recommends an even more cautious three hours.

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