When to take Magnesium
Also known as Magnesium citrate, Magnesium glycinate, Magnesium oxide
Any time; consistency matters more than timing. You can take magnesium with or without food, but high doses and forms like magnesium oxide or carbonate are the most likely to cause loose stools.
Last reviewed October 13, 2026
Timing
| Best time | Any time of day |
|---|---|
| Food | With or without food |
| Fat-soluble | No |
- Any time; consistency matters more than timing.
- Forms that dissolve well in liquid, such as magnesium citrate, aspartate, lactate and chloride, are absorbed better than magnesium oxide or sulfate.
- Very high zinc doses (142 mg a day in one study) can interfere with magnesium absorption. Normal zinc amounts were not shown to do this.
Check with your doctor first if…
- Upper limit: 350 mg a day of magnesium from supplements and medicines for adults (food does not count). Higher doses often cause diarrhea, nausea and stomach cramps.
- Kidney problems: the risk of too much magnesium is higher when your kidneys do not work well. Ask your doctor first.
- Osteoporosis pills (bisphosphonates such as alendronate): take magnesium at least 2 hours before or after them.
- Antibiotics (tetracyclines such as doxycycline, or quinolones such as ciprofloxacin): take the antibiotic at least 2 hours before or 4–6 hours after magnesium.
- Water pills and long-term acid reducers (PPIs) can change your magnesium levels. Tell your doctor if you take them.
Amounts studied
RDA: 400–420 mg a day for men and 310–320 mg a day for women (350–360 mg in pregnancy). UL: 350 mg a day from supplements and medicines (does not include food). Blood pressure trials used about 243–973 mg a day. Note: the label lists elemental magnesium, not the weight of the whole compound.
Follow the serving size on your product’s label.
What the research says
| Area | Evidence | Summary |
|---|---|---|
| Heart health | Limited | In trials, magnesium changed blood pressure only slightly, by about 2–4 mmHg. The FDA has said the evidence is inconsistent and inconclusive.[1] |
| Bone health | Limited | Magnesium helps build bone, and higher intakes are linked to higher bone density in population studies. Few trials have tested supplements, so more research is needed.[1] |
Questions
Should I take magnesium at night?
The NIH fact sheet gives no best time of day, and we found no good evidence that timing matters. Any time; consistency matters more than timing.
Which form of magnesium is absorbed best?
Forms that dissolve well in liquid are absorbed best. Small studies found magnesium citrate, aspartate, lactate and chloride are absorbed better than magnesium oxide or sulfate.
Can I take magnesium with zinc?
Yes, at normal amounts. Only a very high zinc dose (142 mg a day in one study) was found to interfere with magnesium absorption.
Why does magnesium give me diarrhea?
Magnesium that is not absorbed pulls water into the gut. This happens more with high doses and with magnesium carbonate, chloride, gluconate and oxide. Staying at or under 350 mg a day from supplements helps.
Can I take magnesium with antibiotics?
Not at the same time. Take tetracycline or quinolone antibiotics at least 2 hours before or 4–6 hours after magnesium.
Plan your whole routine
Add Magnesium and everything else you take to the planner to see your morning, midday and evening, and what to keep apart.
Open the plannerSources
- Magnesium: Fact Sheet for Health Professionals, NIH ODS (accessed October 13, 2026)
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. It is general information, not medical advice: talk with your doctor or pharmacist before starting a supplement, especially if you are pregnant, breastfeeding, take medicine or have a health condition.