What should you not take with magnesium?

Some medicines call for caution, because magnesium can interfere with how well they are absorbed. Which combination matters, and how long to wait between them, depends on the specific active ingredient and product. A blanket rule like “two hours between everything” can therefore be wrong. [1–4]

The examples below are a starting point for checking against your own package. They are not a complete interaction database and not a personal dosing schedule. Do not stop a prescribed medicine or change its dose on your own because of a supplement.

Four examples that follow different rules

Medicine or group	Why magnesium matters	What the reviewed document says
Certain antibiotics, including tetracyclines and quinolones	Magnesium can form poorly soluble compounds and reduce absorption.	The NIH gives different gaps depending on which is taken first. The specific drug information takes precedence. [1]
Ciprofloxacin, a specific quinolone	The product labeling warns, among other things, about antacids containing magnesium or aluminum.	The reviewed US tablet labeling says to take ciprofloxacin at least two hours before or six hours after these products. The order matters. [2]
Levothyroxine	Antacids containing magnesium can affect absorption.	The reviewed US information gives a four-hour gap from antacids in its patient guidance. This is not a rule verified across the board for every form of magnesium and every German product. [3]
Dolutegravir, here Tivicay	Mineral supplements and antacids can affect absorption.	The EU product information distinguishes antacids from supplements, and taking the drug with or without a meal. Agree on the schedule with your care team. [4]

Oral bisphosphonates for osteoporosis can also be affected. The NIH describes reduced absorption with magnesium-rich products. [1] For any check, then, the medicines need to be known as well, not only the supplements.

Why “before” and “after” are not interchangeable

A timing gap always involves two pieces of information: how long and which product comes first. In the ciprofloxacin example above, two hours after the magnesium product would not be the same arrangement as two hours before it.

Only once the rule for the specific product is clear can it be turned into a reliable schedule. That requires the active ingredient, the formulation and the package leaflet to match. The US information here is clearly labeled as an example; it is not automatically transferred to a German package.

Magnesium is not only found in magnesium capsules

Combination products count too. A list or a photo of every package helps: medicines, antacids, mineral blends and supplements. What matters are the ingredients and the daily amount actually taken.

A single product name can cover several active ingredients. That is why the pharmacy should not just hear “my stomach remedy” or “my sports powder” but see the exact product name. This also helps you avoid accidentally treating two different magnesium sources as if they were one.

And what about zinc, iron or calcium?

Combinations of several minerals raise different questions from drug interactions. Here too, it depends on the compound, its amount and the outcome that was studied.

For the common pairing of zinc and magnesium, our separate overview explains why one study using a very high amount of zinc does not produce a general separation rule for typical products. For iron or calcium, this article deliberately offers no universal timetable. A prescribed treatment requires a check specific to the product.

What details are needed for a reliable answer

1. Name and active ingredient of the medicine, including its dosage form.
2. Name, ingredients and daily serving of the magnesium product.
3. When you have taken them so far, and whether you take them with a meal.
4. Any other medicines and supplements.

With these details, the pharmacy or your care team can check the specific combination. If you have already taken them together, do not take an extra dose of the medicine as a precaution; check with the pharmacy or your care team what to do next.

Sources and scope

1. NIH ODS: Magnesium, section on drug interactions: overview, not German product information.
2. DailyMed: ciprofloxacin tablets: specific US labeling; interactions/administration section.
3. DailyMed: Levothyroxine sodium: specific US labeling; antacids named explicitly.
4. EMA: Tivicay, EU product information: summary of product characteristics and package leaflet; check the product identity.