mineral
Magnesium: Forms, Timing and How Much Per Day
Also known as magnesium citrate, magnesium oxide, magnesium glycinate, magnesium chloride, magnesium supplement, mag
Short answer
Magnesium is a mineral the body uses in more than 300 enzyme systems, including muscle and nerve function. Supplements come as oxide, citrate, chloride and other forms; forms that dissolve well in liquid are absorbed better. The NIH upper limit of 350 mg a day counts supplements and medicines only, not food. High doses can cause diarrhea [1].
Last reviewed · 2 sources
What is Magnesium?
Magnesium is a mineral found in many foods, added to some, sold as a supplement, and present in some antacids and laxatives [1]. The body uses it as a cofactor in more than 300 enzyme systems, including protein synthesis, muscle and nerve function, blood glucose control and blood pressure regulation [1]. It is also needed for energy production, bone structure and making DNA and RNA [1]. About 50% to 60% of the body's magnesium is in the bones [1].
Forms of Magnesium you'll see on labels
Magnesium oxide
A common supplement form. Small studies found it is absorbed less completely than the aspartate, citrate, lactate and chloride forms [1]. It is one of the forms most often reported to cause diarrhea [1].
Magnesium citrate
Small studies found it is absorbed more completely than magnesium oxide and sulfate [1].
Magnesium chloride
Small studies found it is absorbed more completely than oxide and sulfate, but it is also among the forms most often reported to cause diarrhea [1].
Magnesium aspartate and lactate
Small studies found these are absorbed more completely than oxide and sulfate [1].
Magnesium sulfate
Small studies found it is absorbed less completely than the citrate, aspartate, lactate and chloride forms [1].
Magnesium carbonate and gluconate
Among the forms most often reported to cause diarrhea [1].
Magnesium hydroxide
Found in some laxatives and antacids, for example milk of magnesia, rather than as a daily supplement [1].
How much Magnesium do adults need?
NIH lists these Recommended Dietary Allowances (RDA) for adults 19+, from all sources (food, drinks, supplements and medicines). Reference values, not a personal recommendation.
| Group | Amount per day |
|---|---|
| Men 19–30 | 400 mg |
| Men 31+ | 420 mg |
| Women 19–30 | 310 mg |
| Women 31+ | 320 mg |
| Pregnancy 19–30 | 350 mg |
| Pregnancy 31–50 | 360 mg |
| Lactation 19–30 | 310 mg |
| Lactation 31–50 | 320 mg |
Upper limit: 350 mg a day from supplements and medicines for adults, including during pregnancy and lactation. Magnesium in food and drinks is not counted [1].
How Magnesium appears on a label
The Supplement Facts label lists the amount of elemental magnesium, not the weight of the whole compound (such as magnesium citrate) [1]. Amounts are in mg. The Daily Value (DV) used for % DV is 420 mg for adults and children 4 and older [1].
When to take Magnesium
No official source names a best time of day to take magnesium, or says whether to take it with or without food. NIH does give spacing rules for some medicines: take it at least 2 hours apart from oral bisphosphonates, and see the antibiotic note below [1].
What to keep apart from Magnesium
Zinc (high doses)
One study found very high zinc doses from supplements (142 mg a day) can interfere with magnesium absorption [1].
Bisphosphonates (osteoporosis medicines such as alendronate)
Magnesium can reduce their absorption. NIH says taking magnesium at least 2 hours before or after them can minimize this [1]. Ask your pharmacist.
Tetracycline and quinolone antibiotics
Magnesium can bind these antibiotics (for example doxycycline or ciprofloxacin). NIH says to take the antibiotic at least 2 hours before or 4 to 6 hours after magnesium [1]. Ask your pharmacist.
Diuretics
Long-term loop and thiazide diuretics can increase magnesium loss in urine; potassium-sparing diuretics reduce it [1]. Ask your pharmacist.
Proton pump inhibitors (PPIs)
Taking PPIs for a long time (usually more than a year) can cause low blood magnesium [1]. Ask your pharmacist or doctor.
Laxatives and antacids
Some contain magnesium (often as magnesium hydroxide), which adds to your total from supplements [1].
Foods that contain Magnesium
- Pumpkin seeds
- Chia seeds
- Almonds and cashews
- Spinach
- Peanuts and peanut butter
- Black beans and edamame
- Soymilk
- Shredded wheat and fortified cereals
- Brown rice
- Whole wheat bread
- Potato with skin
- Yogurt
Who should ask a doctor or pharmacist first
Talk to a doctor or pharmacist first if you have kidney problems, because the risk of magnesium toxicity rises when the kidneys cannot remove the excess [1]. Also ask first if you take bisphosphonates, tetracycline or quinolone antibiotics, diuretics or proton pump inhibitors [1].
Keep Magnesium in a routine that fits
Supin schedules what you take by time of day, reminds you, and tells you when a bottle runs low.
Magnesium: questions people ask
The NIH fact sheet does not compare glycinate directly. It says forms that dissolve well in liquid are absorbed better, and small studies found citrate is absorbed more completely than oxide [1].
No official source names a best time of day for magnesium. If you take certain antibiotics or bisphosphonates, NIH gives spacing rules to follow [1].
The RDA counts magnesium from all sources, including food. The 350 mg upper limit counts only supplements and medicines, because magnesium in food does not pose a risk in healthy people [1].
NIH notes one study where very high zinc doses (142 mg a day) interfered with magnesium absorption [1]. It does not give a rule for normal doses.
Yes. Supplement Facts labels list elemental magnesium, not the weight of the whole compound [1].
Sources
- Magnesium: Fact Sheet for Health Professionals — NIH Office of Dietary Supplements
- Others - Vitamins and minerals (Magnesium) — NHS
Educational information, not medical advice. The amounts above are official reference values, not a recommendation for you. Check with your doctor or pharmacist before starting or changing supplements, especially if you take medication, are pregnant or have a health condition. Supin sells a subscription, not supplements. Last reviewed .