Magnesium citrate: two very different products with the same name
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- Magnesium citrate oral solution (saline laxative). Best for: Adults needing short-term relief of occasional constipation. See options on Amazon
- Magnesium citrate capsules with a moderate dose. Best for: Adults adding magnesium as a daily supplement. See options on Amazon
- Magnesium citrate powder drink. Best for: Adults who prefer a mixed drink and can measure doses. See options on Amazon
Laxative or supplement? Know which you are buying
| Feature | Laxative (oral solution or powder) | Supplement (tablets, capsules) |
|---|---|---|
| Purpose | Short-term relief of occasional constipation, or bowel prep | Adding magnesium to the diet |
| How it acts | Draws water into the stool | Supplies magnesium; high doses can loosen stools |
| Timing | Usually a bowel movement in 30 minutes to 6 hours | Taken daily, often with food |
| Limit | No more than 1 week unless a doctor advises | Keep supplement magnesium under 350 mg a day |
MedlinePlus describes magnesium citrate as a saline laxative that works by causing water to be retained with the stool, softening it and increasing bowel movements. It is also used to empty the colon before a colonoscopy. A daily supplement is a different product with a different dose.
Using magnesium citrate as a laxative
MedlinePlus says magnesium citrate is used to treat occasional constipation on a short-term basis. It usually causes a bowel movement within 30 minutes to 6 hours.
- Take the liquid with a full 8-ounce (240 mL) glass of liquid.
- Powder is mixed with 10 ounces (296 mL) of cold water or other liquid; discard mixed solution not used within 36 hours.
- Do not use it for more than 1 week unless your doctor tells you to.
- Take other medicines at least 2 hours before or after it.
Stop and call your doctor if you have blood in your stool or cannot have a bowel movement after using it. Tell your doctor first if you have kidney disease, are on a magnesium- or sodium-restricted diet, or have stomach pain, nausea, vomiting or a sudden change in bowel habits lasting more than 2 weeks.
Using magnesium citrate as a daily supplement
NIH explains that the Supplement Facts panel lists elemental magnesium, and that forms that dissolve well in liquid, such as citrate, are absorbed more completely in the gut than less soluble forms.
As a label example, NOW Magnesium Citrate tablets list a serving of 2 tablets with 400 mg of elemental magnesium, taken daily with food. That one serving is above NIH's adult upper limit of 350 mg a day of magnesium from supplements and medicines, so it is a case for reading the label before following it. NOW's label is for adults only, with physician consultation if pregnant or nursing, taking medication or living with a medical condition.
NIH lists adult RDAs of 310 to 420 mg a day from all sources, including food. Many people need only a modest supplement amount, if any. For other forms, see our magnesium malate guide and magnesium L-threonate guide.
Magnesium citrate vs glycinate
Both are commonly sold forms. NIH says forms that dissolve well in liquid are more completely absorbed, but it does not name one form as best for every purpose. Citrate's tendency to pull water into the gut is useful in a laxative but can mean loose stools in a supplement. Whatever the form, the elemental magnesium amount and your total from all supplements matter most.
Side effects and who should be careful
NIH says high magnesium intake from supplements or medicines can cause diarrhea, nausea and abdominal cramping. The risk of magnesium toxicity rises with impaired kidney function, because the kidneys cannot remove the excess. Very high doses can cause low blood pressure, vomiting, difficulty breathing and irregular heartbeat.
Magnesium can interfere with oral bisphosphonates and tetracycline or quinolone antibiotics; MedlinePlus advises taking other medicines at least 2 hours apart from magnesium citrate. Ask a pharmacist about your exact medicines, and tell your doctor if you are pregnant or breastfeeding.
How to choose
- For occasional constipation: a magnesium citrate oral solution, used short term as labeled.
- For daily magnesium: tablets or capsules with a clear elemental magnesium amount, kept under 350 mg a day from all supplements.
- Check serving size; many supplements need 2 or more units for the listed amount.
- Kidney disease? Ask your doctor before any magnesium product.
- Look for a verifiable quality mark such as USP or NSF.
What to look for when you buy
Magnesium citrate oral solution (saline laxative)
Best for: Adults needing short-term relief of occasional constipation
MedlinePlus says it usually works within 30 minutes to 6 hours by drawing water into the stool.
Watch out: No more than 1 week unless your doctor says so. Not for people with kidney disease without medical advice.
See options on AmazonMagnesium citrate capsules with a moderate dose
Best for: Adults adding magnesium as a daily supplement
Citrate is a soluble form that NIH notes is well absorbed. A capsule with a clear elemental amount helps you stay under 350 mg a day.
Watch out: Count magnesium from other supplements, antacids and laxatives; citrate can loosen stools.
See options on AmazonMagnesium citrate powder drink
Best for: Adults who prefer a mixed drink and can measure doses
Powder lets you take a smaller amount. Read elemental magnesium per scoop and mix as directed.
Watch out: Check whether the product is a supplement or a laxative-strength powder before using it daily.
See options on AmazonQuestions people ask
- How long does it take for magnesium citrate to work?
- As a laxative, MedlinePlus says it usually causes a bowel movement within 30 minutes to 6 hours. As a daily supplement, it is not meant to have a quick effect.
- What is magnesium citrate good for?
- Short-term relief of occasional constipation and bowel prep (as a laxative), or adding magnesium to your diet (as a supplement).
- How much magnesium citrate should I take?
- Follow the product label. For daily supplements, NIH's limit is 350 mg of magnesium a day from supplements and medicines, not counting food.
- Can I take magnesium citrate every day?
- The laxative is for short-term use, up to a week unless your doctor advises. A supplement-strength product can be daily if you stay under 350 mg of supplemental magnesium and your kidneys are healthy.
Sources
- Magnesium Citrate: MedlinePlus Drug Information (medlineplus.gov), MedlinePlus, National Library of Medicine
- Magnesium: Fact Sheet for Health Professionals (ods.od.nih.gov), NIH Office of Dietary Supplements
- Magnesium Citrate Tablets (www.nowfoods.com/products/supplements/magnesium-citrate-200-mg-tablets), NOW Foods