Magnesium citrate usually causes a bowel movement within 30 minutes to 6 hours after you take it. The timing depends on the product, dose, hydration, and your digestive system.
Magnesium Citrate Timing at a Glance
| Question | Answer |
|---|---|
| When does magnesium citrate start working? | Usually within 30 minutes to 6 hours |
| How does it work? | It draws water into the stool, making bowel movements softer and easier to pass |
| What should you do while waiting? | Follow the product directions and stay near a bathroom |
| Should you take more if it has not worked yet? | No. Do not exceed the label directions without medical advice |
| How long should you use it? | Use it for occasional constipation and no longer than 1 week unless a clinician advises otherwise |
Why Does Magnesium Citrate Work So Quickly?
Magnesium citrate is a saline laxative. It draws water into the stool, which increases moisture and can help trigger a bowel movement. This usually makes magnesium citrate work faster than bulk-forming fiber supplements, which can take longer to affect bowel movements.
What Should You Do If Magnesium Citrate Has Not Worked After 6 Hours?
Do not take another dose automatically. Check the product label or contact a pharmacist or healthcare professional, especially if you have abdominal pain, nausea, vomiting, kidney disease, or have already taken another laxative.
The official magnesium citrate label says to stop using it and ask a doctor if you have rectal bleeding or do not have a bowel movement after taking it.
How Should You Take Magnesium Citrate Safely?
- Follow the instructions on your bottle. Magnesium citrate products can have different concentrations and dosing instructions.
- Drink the recommended full glass of liquid with the dose. Many oral solutions tell adults to take the dose with 8 ounces of liquid.
- Take magnesium citrate at least 2 hours before or 2 hours after other medicines, unless a pharmacist or doctor gives you different instructions.
- Do not use magnesium citrate for more than 1 week unless a healthcare professional tells you to do so.
Who Should Ask a Doctor Before Taking Magnesium Citrate?
Ask a doctor before taking magnesium citrate if you have:
- Kidney disease
- Abdominal pain, nausea, or vomiting
- A magnesium-restricted diet
- A sudden change in bowel habits lasting more than 2 weeks
- Pregnancy or are breastfeeding
- Ongoing constipation or a repeated need for laxatives
Magnesium citrate is for occasional constipation. It is not intended as a regular, long-term treatment.
What If You Are Using Magnesium Citrate for a Colonoscopy?
If a clinician prescribed magnesium citrate or another bowel-cleansing preparation before a colonoscopy, follow the instructions for your procedure. Colonoscopy preparation may use a different schedule and require additional fluids, so do not use the general 30-minute-to-6-hour window in place of your healthcare provider's instructions.
Magnesium citrate generally works within 30 minutes to 6 hours. If you do not have a bowel movement after taking it, do not repeat the dose without medical advice, especially if you have pain, vomiting, bleeding, or kidney disease.