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A Clinical Note From Dr. Adegbola
Not All Magnesium Helps With Constipation
The form your bottle says matters more than the dose on the label.
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One of my patients came in last month with a familiar complaint. "I'm already taking magnesium every night. 400 milligrams. The constipation hasn't changed."
I asked which form. Magnesium glycinate, she said. Her functional medicine practitioner recommended it for sleep.
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Here's the problem: glycinate is one of the most absorbable forms of magnesium. Your small intestine pulls it into your bloodstream before it ever reaches your colon. That's good for sleep. It's useless for constipation. |
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Your colon needs magnesium that stays in the gut. When magnesium reaches your large intestine, it creates an osmotic gradient. Water gets pulled into the colon, softening stool and triggering the smooth muscle contractions that move things along. |
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40%
On a GLP-1 medication, calorie intake can drop by up to 40%, meaning roughly 40% less magnesium from food. Your gut is already moving slower from the medication itself. Two problems, stacking on top of each other.
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Which forms work for constipation |
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Magnesium citrate (200–400mg before bed), the most studied form for constipation. Enough reaches your colon to draw water in, but it absorbs gently enough to avoid cramping. |
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Magnesium oxide (400–800mg daily), less absorbed overall, which sounds like a downside but is the point. More of it stays in your gut, creating a stronger osmotic effect. |
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Which forms won't help constipation |
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Magnesium glycinate, great for sleep and anxiety, fully absorbed before it reaches the colon. |
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Magnesium threonate, crosses the blood-brain barrier for cognitive support, minimal GI effect. |
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Magnesium taurate, cardiovascular support, not a GI mover. |
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Two things I tell patients in clinic |
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Start low, go slow.
Begin with 200mg of magnesium citrate before bed. Increase by 100mg every 3–4 days until you find the dose that produces soft, easy-to-pass stools without loose stool. Everyone's threshold is different. |
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Pair it with a soluble fiber that holds water.
Magnesium pulls water into the colon. Psyllium holds that water in the stool so it doesn't just pass through. The combination works better than either alone. |
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That patient switched from glycinate (kept it for sleep) and added 300mg citrate at bedtime. Within four days, she texted my office:
"First normal morning in two months."
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If your current approach to GLP-1 constipation isn't working, the answer might not be more fiber or more water. It might be the right mineral, in the right form, reaching the right place. |
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To your gut health,
Dr. Onikepe Adegbola, MD PhD
Founder, Casa de Sante
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