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The right amount of magnesium citrate is different for constipation and daily supplementation.
| Purpose | Typical guidance for adults |
|---|---|
| Occasional constipation | Follow the bottle's laxative directions. One current U.S. label for adults and children 12 and older lists 6.5 to 10 fluid ounces, with a maximum of 10 fluid ounces in 24 hours. |
| Daily magnesium supplement | Check the label for elemental magnesium. Unless a healthcare professional recommends otherwise, do not routinely exceed 350 mg per day from supplements or magnesium-containing medicines. |
For Constipation: How Much Magnesium Citrate Should I Take?
For occasional constipation, follow the directions on your bottle. One U.S. label for adults and children 12 and older lists 6.5 to 10 fluid ounces, with no more than 10 fluid ounces in 24 hours. Drink a full 8-ounce glass of liquid with the dose. Concentrations vary by product, so use the instructions for your specific bottle.
Magnesium citrate usually causes a bowel movement within 30 minutes to 6 hours. Use it only for occasional constipation, and do not take it for more than one week unless your doctor tells you to.
A laxative dose is not the same as a daily magnesium supplement. Magnesium citrate laxative solutions contain much more magnesium than typical nutritional supplements because they draw water into the stool.
For a Daily Magnesium Supplement: How Much Should I Take?
For daily supplementation, use the amount of elemental magnesium listed in the Supplement Facts panel. Do not use the total weight of "magnesium citrate" elsewhere on the label to calculate your dose.
For healthy adults, total magnesium intake from food, beverages and supplements is generally 310 to 420 mg per day, depending on age and sex. The upper limit of 350 mg per day applies only to magnesium from supplements and medicines, not magnesium naturally found in food.
Higher amounts can cause diarrhea, nausea and abdominal cramping. Very high doses can cause magnesium toxicity, especially in people with impaired kidney function.
When Should I Avoid Magnesium Citrate or Ask a Doctor First?
Ask a doctor or pharmacist before taking magnesium citrate if you:
- Have kidney disease
- Are pregnant or breastfeeding
- Take prescription medicines or other supplements
- Have stomach pain, nausea, vomiting or a recent change in bowel habits
- Need magnesium citrate to prepare for a colonoscopy or another procedure
Magnesium citrate can interfere with other medicines. MedlinePlus advises taking other medicines at least 2 hours before or 2 hours after magnesium citrate, unless your pharmacist gives you different instructions.
Stop using magnesium citrate and seek medical advice if you have blood in your stool or cannot have a bowel movement after taking it.