Quick answer

Ask your pharmacist or doctor before combining. Drug labels document 4 supplements for tetracycline antibiotics such as doxycycline: calcium, iron, magnesium and multivitamins. They say minerals can keep the antibiotic from being absorbed, so spacing matters, and your pharmacist can set it for your own product.^1,2,3

Key facts

The doxycycline label says antacids containing aluminum, calcium or magnesium, and iron-containing preparations, impair the absorption of tetracyclines.¹
The tetracycline label adds zinc to that list, and says food and some dairy products also interfere with its absorption.³
NIH's magnesium and zinc fact sheets both describe the problem: magnesium can form insoluble complexes with tetracyclines, and zinc supplements should be separated from them.^4,5
MedlinePlus's doxycycline page gives spacing advice for antacids, calcium supplements, magnesium laxatives, iron preparations and vitamin products that contain iron.²
All 4 entries on this page are printed on drug labels and carry the severity separate doses, not avoid.^1,6,7,8

What are tetracycline antibiotics, and why do minerals matter?

Doxycycline, minocycline and tetracycline itself belong to this class. MedlinePlus describes doxycycline as a medicine for bacterial infections and certain infections spread by ticks, lice, mites and animals, for malaria prevention in travelers, and for acne and rosacea, and it places the drug in a class called tetracycline antibiotics.²

Minerals matter because of how these antibiotics reach the blood. NIH's magnesium fact sheet says magnesium can form insoluble complexes with tetracyclines such as doxycycline, and the labels describe the result as impaired absorption. Less absorbed antibiotic is the concern the labels raise.^1,4

Do calcium, magnesium and iron supplements interfere with tetracycline antibiotics?

Ask your pharmacist how far apart to take them

Calcium can keep tetracycline antibiotics from being absorbed. The doxycycline label says antacids containing calcium impair the absorption of tetracyclines.¹

On the medicine's label

The calcium card rests on the antacid wording in the doxycycline label, so a calcium supplement and a calcium antacid fall under the same sentence. MedlinePlus names calcium supplements on its doxycycline page as well.^1,2

Ask your pharmacist how far apart to take them

Tetracycline antibiotics such as doxycycline may not be absorbed if taken too soon before or after a product that contains magnesium. The doxycycline label says antacids containing magnesium impair the absorption of tetracyclines.^7,9,10

On the medicine's label

The magnesium card adds NIH's own fact sheets to the label. Magnesium is also found in some laxatives, and MedlinePlus lists laxatives containing magnesium by name for doxycycline.^2,10

Ask your pharmacist how far apart to take them

Iron can keep tetracycline antibiotics such as doxycycline from being absorbed. The doxycycline label says iron-containing preparations impair the absorption of tetracyclines.⁶

On the medicine's label

Iron reaches furthest, because the label wording covers iron-containing preparations in general, and MedlinePlus names vitamin products that contain iron.^2,6

Does a multivitamin or zinc matter with tetracycline antibiotics?

Ask your pharmacist how far apart to take them

Tetracycline antibiotics such as doxycycline are absorbed less when taken close to products that contain calcium, magnesium, iron or zinc. Their labels say antacids with calcium or magnesium and iron-containing preparations impair absorption, the tetracycline label adds zinc, and MedlinePlus names vitamin products that contain iron.^{3,4,5,8,11,12}

On the medicine's label

A multivitamin can carry several of these minerals at once, so it is the card most likely to catch someone who thinks only of a calcium or iron pill. The tetracycline label adds zinc to the list, while the doxycycline label names calcium, magnesium and iron, so the exact antibiotic matters.^3,8

Labels also differ on food. The tetracycline label says food and some dairy products interfere with absorption, while the doxycycline label says its absorption is not markedly influenced by food or milk. Your pharmacist can tell you which statement applies to your prescription.^3,8

Why do these entries say separate doses instead of avoid?

Every card on this page carries the same two tags: the severity separate doses and the basis on the label. In this page's vocabulary, separate doses means the sources describe a spacing problem. They do not describe a reason to give up the supplement for good, and they do not give one universal gap, because the right spacing depends on the antibiotic, the product and your schedule. This page therefore gives no times.

The other two basis tags used on this site, studies and expected, do not appear here. All 4 entries are printed on drug labels, so none of them is a theoretical concern.^1,3

What to ask your pharmacist about tetracycline antibiotics and supplements

Is my antibiotic a tetracycline such as doxycycline or minocycline, or from another class?
Which of my supplements contain calcium, magnesium, iron or zinc?
How should I schedule the antibiotic around them for the whole course?
Do the antacids and magnesium laxatives I buy over the counter count as well?²

If your antibiotic belongs to another class, such as amoxicillin, the sources on this page do not address it. That is not a finding either way, so ask your pharmacist.

Questions people ask

What supplements should I avoid with tetracycline antibiotics?

Calcium, iron, magnesium and multivitamin products are documented, because the minerals in them can keep the antibiotic from being absorbed. The labels describe separating doses, not giving up the supplement, so ask your pharmacist how to space them.^1,3

Which vitamins should I not take with tetracycline antibiotics?

Vitamin products matter when they contain minerals such as iron, calcium, magnesium or zinc, and MedlinePlus names vitamin products that contain iron for doxycycline. The sources on this page do not address vitamins without those minerals, which is not a finding either way, so ask your pharmacist.^2,3

Which supplements interact with tetracycline antibiotics?

The 4 entries on this page: calcium, iron, magnesium and multivitamins, which carry several minerals together. All 4 are on drug labels, and the tetracycline label also lists zinc.^1,3,6

Does this apply to doxycycline and minocycline?

Both labels use the same wording: antacids containing aluminum, calcium or magnesium, and iron-containing products, impair the absorption of tetracyclines. Ask your pharmacist about the exact medicine you were given.^8,11

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Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.