ImportantThis page is general information, not a prescription. Don't start, stop, or change a medicine without talking to your provider or pharmacist.
Overview
It's poorly absorbed, which is why it can loosen stools.
What it's used for
- Low magnesium
- Off-label: migraine prevention
- Constipation and heartburn
How to take it
- Take with food to lower stomach upset.
Your dose depends on your health and other medicines. Always follow your prescription label, and ask your pharmacist if anything is unclear.
Side effects
Common side effects
- Diarrhea
- Upset stomach
Call your provider todayWeakness, slow heartbeat, or confusion (too much magnesium, mainly with kidney disease)
Warnings
- Ask a provider first if you have kidney disease.
Other medicines, foods, and alcohol
- Separate from antibiotics like doxycycline and ciprofloxacin, levothyroxine, and bisphosphonates by several hours.
Tell your provider and pharmacist about every medicine, vitamin, and supplement you take.
Pregnancy and breastfeeding
Ask your provider.
Missed doses, overdose, and storage
If you miss a dose
Take it as soon as you remember, unless it's almost time for your next dose. Then skip the missed dose. Don't take two doses at once.
If someone takes too much
Call Poison Control at 1-800-222-1222 or get help online at poison.org. Call 911 if the person collapses, has a seizure, has trouble breathing, or can't be woken.
Storing it
Store at room temperature, away from heat and moisture (not in the bathroom), and out of reach of children and pets.
Conditions it's used for
Sources
- DailyMed: FDA drug label for Magnesium oxide (U.S. National Library of Medicine)
- MedlinePlus: Drugs, herbs, and supplements
- FDA: Drugs@FDA
Last updated 2026-11-13.