Magnesium and vitamin B6: the benefits, how to take it and how much B6 is too much

What magnesium B6 is and why people take it

Magnesium B6 combines a magnesium salt (usually lactate or citrate) with vitamin B6 (pyridoxine). In some countries it’s sold in pharmacies as a licensed medicine; on iHerb and in UK shops it’s a food supplement. Doses differ a lot.

Pharmacy versions are meant to correct low magnesium: the instructions for one of them say to stop once blood magnesium returns to normal. True magnesium deficiency is uncommon in healthy people who eat well, because the kidneys hold on to magnesium when intake is low. Our guide to magnesium deficiency symptoms explains who is at risk.

Most people buy magnesium B6 without a test, hoping for one of these benefits:

• less stress and irritability;
• better sleep;
• fewer muscle cramps and twitches;
• milder premenstrual symptoms.

None of these has strong evidence behind the combination. The table below shows what the trials actually found.

Why is vitamin B6 added to magnesium?

In theory, B6 helps magnesium get into cells and stay in the body. Clinical evidence for this is thin.

Best known is a 2018 comparison trial published in PLoS One. 264 adults with stress and low blood magnesium took either 300 mg of magnesium plus 30 mg of B6, or 300 mg of magnesium alone, for 8 weeks. Stress scores on the DASS-42 scale fell in both groups (by 45% and 42%), with no significant difference between them. Only in people with severe stress did the B6 combination do about 24% better, and that was a subgroup finding. There was no placebo group, so we can’t tell how much of the effect came from magnesium itself.

How much B6 is in a tablet, and why it matters

With magnesium B6, the real issue is the pyridoxine dose, not the magnesium. The NHS advises taking no more than 10 mg of B6 a day from supplements unless a doctor tells you to. In 2023 EFSA lowered its safe upper limit for adults, including pregnant and breastfeeding women, to 12 mg a day from all sources, food included.

Say you bought a pack of “forte” tablets at a pharmacy abroad and followed the instructions to the letter. That’s 30–40 mg of B6 a day. So the treatment dose gives 2.5–3.3 times Europe’s B6 limit, plus about 290–400 mg of magnesium against EFSA’s 250 mg for supplements. That’s acceptable for a short course under medical supervision. It isn’t a sensible “just in case” routine for months.

Too much B6 over a long time can cause peripheral neuropathy, which is damage to the nerves in the hands and feet. Typical signs:

• numbness and tingling in the feet and hands;
• burning or “pins and needles” in the legs;
• unsteadiness when walking;
• reduced feeling in the skin.

According to the NHS, 200 mg a day or more for a long time can cause loss of feeling in the arms and legs, which may be permanent. It adds that the effects of 10–200 mg are unclear. If you notice early signs, stop taking it and see your GP. Our B vitamins guide shows how B6 adds up across supplements.

Work out how much B6 your magnesium tablets give you:

For B complexes and multivitamins, use the separate B6 toxicity checker.

How to take magnesium B6

• Take the tablets with food to lower the chance of nausea and loose stools.
• Split the daily dose into 2–3, as pharmacy instructions do. Smaller single doses of magnesium are gentler on the gut.
• Keep iron, calcium and phosphates apart: according to the instructions, they reduce magnesium absorption.
• Add up B6 from magnesium tablets, B complexes and multivitamins.
• Stay within the magnesium limit. EFSA considers up to 250 mg a day from supplements safe; the NHS says 400 mg or less is unlikely to cause harm.

If you’re not on a pharmacy course and just want extra magnesium, 100–200 mg a day is enough for most people. Magnesium from food doesn’t count towards the supplement limit.

How long can you take magnesium B6?

There’s no single rule, but the instructions and safety limits point the same way:

1. Treatment dose (30–40 mg of B6 a day): about a month. Instructions for the “forte” tablets say treatment usually lasts 1 month; the standard ones say to stop once blood magnesium is normal.
2. After the course, decide with your GP whether you still need magnesium. If nothing changed after a month, repeating the same routine makes little sense.
3. For months of use, choose a product with no more than 10 mg of B6 per daily serving, or one without B6. Most people get enough B6 from food: the NHS puts adult needs at 1.4 mg a day for men and 1.2 mg for women.

If you want magnesium long-term, switch to magnesium glycinate or magnesium citrate without B6. For all forms side by side, see types of magnesium compared.

Magnesium B6 “forte”: what’s different

“Forte” tablets contain twice the active ingredients: 100 mg of magnesium as citrate and 10 mg of B6. A standard tablet has 48 mg of magnesium as lactate and 5 mg of B6. You take fewer tablets, but the daily doses in the instructions are almost the same. Forte isn’t any safer.

Interactions and who should avoid it

• Levodopa (for Parkinson’s disease). B6 at 5 mg or more weakens it. The instructions allow the combination only when levodopa comes with a decarboxylase inhibitor (as in co-careldopa).
• Tetracycline antibiotics. Take magnesium B6 at least 3 hours after the antibiotic.
• Quinolone antibiotics (ciprofloxacin, levofloxacin). Take the antibiotic at least 2 hours before or 6 hours after magnesium.
• Bisphosphonates for osteoporosis. Separate by at least 2 hours.
• Anti-seizure medicines (phenytoin, phenobarbital). High-dose B6 may lower their blood levels, so ask your doctor.
• Other B6 supplements. Check B complexes, multivitamins and “nerve” or “PMS” formulas.

Our vitamin compatibility chart shows which other supplements shouldn’t be taken together.

Who needs medical advice first:

• Severe kidney disease. Magnesium can build up.
• Pregnancy. Only on a doctor’s or midwife’s advice.
• Breastfeeding. Magnesium passes into breast milk.
• Children. Doses depend on age and weight; follow a paediatrician.
• Lactose intolerance. Some tablets contain lactose.

Run through this list before you buy; it takes a minute:

Signs of too much magnesium include nausea, severe diarrhoea, weakness and an irregular heartbeat. Stop taking it and get medical advice.

How to choose magnesium B6 on iHerb

1. Decide whether you need B6 at all. If you just want more magnesium, choose a form without it.
2. Find the Vitamin B6 line in the Supplement Facts panel. For long-term use, keep it at 10 mg or less per daily serving.
3. Check elemental magnesium per serving and how many tablets that serving is. Stay within 250 mg of magnesium from supplements.
4. Check your other supplements: B6 often hides in multivitamins and B complexes.
5. Compare the price per daily serving in £ or €, not per bottle, and plan how long you’ll take it.

Our Supplement Facts guide explains how to tell compound weight from elemental magnesium.