Quick answer

Ask your pharmacist or doctor before combining. Three tetracycline labels, for doxycycline, tetracycline and minocycline, say absorption of tetracyclines is impaired by iron-containing preparations. MedlinePlus pages for doxycycline and tetracycline name iron and vitamin products that contain iron, and the waiting times they give differ between the two medicines.^1,2,3,4,5

Key facts

The doxycycline label says absorption of tetracyclines is impaired by antacids containing aluminum, calcium or magnesium, and by iron-containing preparations.¹
The tetracycline label lists preparations containing iron, zinc or sodium bicarbonate, and says food and some dairy products also interfere.²
The minocycline label names iron-containing products in its interactions section, and its patient information lists them among the things to tell your doctor about.³
MedlinePlus names iron preparations and vitamin products that contain iron on both its doxycycline and its tetracycline pages, with different waiting times.^4,5
NIH's iron fact sheets do not mention tetracyclines, so this pairing rests on the labels and MedlinePlus.^6,7

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.¹

On the medicine's label

What do the tetracycline labels say about iron?

Iron in three tetracycline labels^1,2,3
Label	What it says about iron	Other products it names
Doxycycline	Absorption of tetracyclines is impaired by iron-containing preparations.	Antacids containing aluminum, calcium or magnesium, and bismuth subsalicylate.
Tetracycline	Absorption of tetracycline is impaired by preparations containing iron.	Antacids containing aluminum, calcium or magnesium, zinc, sodium bicarbonate, and food and some dairy products.
Minocycline	Absorption of tetracyclines is impaired by iron-containing preparations, and the patient information lists iron-containing products to tell your doctor about.	Antacids containing aluminum, calcium or magnesium.

Why would iron lower how much antibiotic the body absorbs?

The labels state the result, impaired absorption, and do not describe the mechanism in the lines quoted here. What follows from the result is simple: an antibiotic that is absorbed less may reach a lower level in the blood than its prescriber intended. The prescriber picked the antibiotic and its schedule for a reason.^1,2,3

MedlinePlus asks people to tell their doctor and pharmacist about the vitamins and nutritional supplements they take, and says the doctor may need to change doses or monitor you carefully.^4,5

Where does iron turn up besides iron tablets?

MedlinePlus names iron preparations and vitamin products that contain iron. NIH says iron is available in many multivitamin and mineral supplements as well as in iron-only supplements, so a multivitamin can contain iron even when you do not think of it as an iron product.^4,5,6

NIH also says iron in supplements is often in the form of ferrous sulfate, ferrous gluconate, ferric citrate or ferric sulfate, and that products for men or seniors frequently contain less iron or none. Check the panel for any of those names before you assume a product has no iron.^6,7

Do the MedlinePlus waiting times match each other?

No. MedlinePlus gives iron its own waiting time on its doxycycline page and another on its tetracycline page, and it gives antacids, calcium and magnesium laxatives different times again. The label lines quoted above give no waiting time. So there is no single rule across the class, and this page does not repeat any of the figures.^4,5

The right gap depends on which tetracycline you take, how often you take it, and what else is on your list. Your pharmacist can give you one schedule that covers all of it.

Does this apply to other antibiotics?

The labels on this page are for tetracycline-class antibiotics. The sources checked do not address other groups, such as penicillin-type antibiotics. That is not a finding either way, so ask your pharmacist about the antibiotic you have.

Is my antibiotic a tetracycline, and does my multivitamin contain iron?
How should I fit iron, antacids, calcium and zinc around each antibiotic dose?
If I miss a dose or start iron mid-course, who should I tell?

Questions people ask

Can you take iron with doxycycline?

Ask your pharmacist or doctor first. The doxycycline label says iron-containing preparations impair the absorption of tetracyclines, and MedlinePlus asks people to space iron products from doxycycline.^1,4

Does iron affect tetracycline antibiotics such as minocycline?

The minocycline label says the absorption of tetracyclines is impaired by iron-containing preparations, and it lists iron-containing products in its patient information.³

Does the iron in a multivitamin matter with tetracycline antibiotics?

MedlinePlus names vitamin products that contain iron on both its doxycycline and tetracycline pages, so a multivitamin with iron belongs in the conversation with your pharmacist.^4,5

Do antacids and calcium matter for tetracycline antibiotics and iron?

The labels also name antacids containing aluminum, calcium or magnesium, and the tetracycline label names zinc and sodium bicarbonate. Tell your pharmacist about all of them.^1,2

Does this apply to amoxicillin?

The labels here are for tetracyclines and do not address amoxicillin. That is not a finding either way, so ask your pharmacist about your own antibiotic.¹

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Sources

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