Vitamin compatibility chart: which vitamins should not be taken together

How to use the vitamin compatibility chart

The chart covers 10 supplements and substances that people most often take together. They are magnesium, zinc, iron, calcium, vitamins D and C, omega-3 and copper, plus coffee or tea and levothyroxine (thyroid hormone). Find the row for one supplement and the column for the other. The colour of the cell gives the answer:

• green – fine to take at the same time;
• amber – take them at different times; the note gives the gap;
• red – possible harm at high doses or with long-term use, so ask a professional.

Tap a cell and the explanation appears below the chart. Everything assumes adults and usual supplement doses.

Vitamins that should not be taken together

There are hardly any strict bans among vitamins. But a few pairs get in each other’s way, and spacing them out helps.

Iron has the most restrictions. If you take it, choose a single-ingredient product and keep it away from calcium, coffee and tea. Vitamin C, on the other hand, helps: it improves absorption of non-haem iron, the type found in plants and supplements. For forms and doses, see our guide to iron tablets and the best iron supplement.

Supplements that work well together

These pairs can happily share one dose:

• iron and vitamin C: vitamin C improves iron absorption;
• vitamin D and magnesium: magnesium is needed to make the active form of vitamin D;
• vitamin D and calcium: calcium is poorly absorbed from the gut without vitamin D;
• vitamin D and omega-3: both are best taken with a meal containing fat;
• calcium and magnesium: they’re often combined in one tablet.

Calcium has one quirk: it’s absorbed best in doses of 500 mg or less. Split a larger dose into two. For choosing a calcium form with vitamin K2, read our calcium and vitamin K2 guide. The NHS advises 10 mcg (400 IU) of vitamin D a day in autumn and winter; more in our vitamin D3 dosage guide.

Can you take magnesium and zinc together?

Yes. You’ll often read that they compete for absorption, but the NIH sources only describe a problem at a very high zinc dose of 142 mg a day. That’s nearly ten times a normal 10–15 mg supplement.

The real issue with zinc is copper. Taking 50 mg of zinc or more for weeks blocks copper absorption, which can lead to anaemia and nerve damage. That’s why a sensible zinc dose is 10–15 mg; see our zinc dosage guide. The forms of magnesium and how well they’re tolerated are covered in magnesium glycinate vs citrate.

Compatibility myths

• “Vitamin C destroys B12.” Early reports of lower B12 and copper with vitamin C were largely due to lab assay errors. Later studies didn’t confirm them.
• “Coffee washes out calcium.” Caffeine reduces calcium absorption only slightly. There’s no need to separate them.
• “Every supplement should be taken on its own.” For most pairs this is unnecessary. Only the amber pairs in the chart need spacing.
• “Magnesium and calcium cancel each other out.” At usual doses they’re sold in the same tablet. Just keep each calcium dose at 500 mg or less.

Supplement and medicine interactions

Medicines interact with supplements far more than vitamins interact with each other. If you take anything regularly, show this table to your GP or to the pharmacist who hands over your prescription.

For B12 and metformin, see our guide to vitamin B12; for omega-3 doses, see how to choose fish oil.

For the most common medicines, the gap is quicker to look up here:

How to build a supplement schedule

1. List everything you take: medicines, vitamins, multivitamins, powders and electrolytes.
2. If you take levothyroxine, take it first thing on an empty stomach with water. Wait at least 60 minutes before coffee.
3. Move iron to at least 4 hours after levothyroxine. You can take it with orange juice for vitamin C, but not with coffee or tea.
4. Keep calcium and magnesium for the evening. Take vitamin D and omega-3 with your main meal.
5. During a course of antibiotics, follow the leaflet: minerals usually move to 4–6 hours after the tablet.
6. If the timings don’t fit your day, ask your pharmacist to help.

When to speak to a doctor or pharmacist

• You take thyroid hormones, anticoagulants, osteoporosis medicines or antibiotics.
• You take 50 mg of zinc or a treatment dose of iron for more than a few weeks.
• You have kidney disease: minerals are cleared less well and can build up.
• You’re pregnant or breastfeeding.

How to choose supplements on iHerb that are easy to combine

1. If something needs to be taken separately, choose single-ingredient products: iron, calcium and magnesium in separate bottles.
2. Check your multivitamin: it often already has iron, calcium and zinc in one tablet.
3. Add up zinc and iron from every bottle.
4. Look for the elemental mineral dose in the Supplement Facts panel, not the weight of the compound. Our supplement label guide shows how.