Last updated: June 2026
Constipation affects around 1 in 7 adults and up to 1 in 3 children in the UK at any given time. While many over-the-counter options exist, magnesium is one of the most widely used natural remedies — backed by clinical evidence and often recommended as a first-line gentle option.
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What causes constipation?
Constipation can be triggered by low fibre intake, dehydration, certain medications or medical conditions (IBS, hypothyroidism), and stress. Research shows that 77% of chronic constipation sufferers found relief when fibre intake was increased, and studies have confirmed that dehydration significantly increases constipation risk.
Read more: CBD oil for IBS | Magnesium for bloating
Does magnesium make you poop?
Yes — magnesium can make you poop. A study published in the European Journal of Clinical Nutrition found that magnesium supplementation significantly increased the frequency of bowel movements and improved stool consistency in constipated patients. Another study in the Journal of Parenteral and Enteral Nutrition confirmed magnesium supplementation effectively treated constipation in hospitalised patients.
How does magnesium help with constipation?
Magnesium relaxes the muscles of the digestive tract, making it easier to pass stools. It also increases the water content in the intestines — drawing fluid into the colon, softening stools and making them easier to move.
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Two forms are most commonly used for constipation — both are osmotic laxatives:
Magnesium citrate
The most well-researched and generally preferred option. Magnesium citrate is highly bioavailable and has a reliable laxative effect by drawing water into the intestines. It’s often the first recommendation, though its effect can be quite strong — medical professionals often suggest trying a gentler stool softener first for mild constipation.
Magnesium oxide
Used for many years as a laxative, particularly in East Asia. Less bioavailable than citrate but effective for constipation in appropriate doses. Requires careful dosing and medical oversight, particularly in older adults or those with kidney conditions.
Note: for general magnesium supplementation alongside sleep and wellbeing support, glycinate and L-threonate are gentler forms less likely to cause loose stools. See our Magnesium Sleep Blend.
Read more: 12 types of magnesium supplements
How much magnesium should you take for constipation?
Studies have found beneficial effects at doses ranging from 125–600 mg/day. NHS guidance states that 400 mg/day or less from supplements is unlikely to cause harm for most adults. Always follow the product label and consult a healthcare professional — the right dose depends on your age, weight, gender and the severity of your symptoms.
Side effects of magnesium for constipation
The most common side effect is diarrhoea — which is also the mechanism that relieves constipation. Other possible side effects include nausea, stomach cramps and bloating. Very high doses can cause low blood pressure or irregular heartbeat. Stick within daily guidance and speak to a professional if side effects persist.
Can magnesium cause constipation?
In rare cases, yes — particularly if taken in excess. Magnesium can have a binding effect on stools at very high doses, leading to slower bowel movements. Stick to recommended amounts and the gentlest effective form for your needs.
Frequently asked questions
Is magnesium citrate good for constipation?
Yes — magnesium citrate is commonly used as an osmotic laxative and is one of the most researched forms for constipation relief. Its effect can be quite strong; clinicians often suggest a gentler stool softener first for mild symptoms.
How fast does magnesium work for constipation?
Many people experience effects within 1–4 hours of taking magnesium citrate, though individual response varies by dose, form and digestive health.
Is it safe to take magnesium daily for constipation?
Short-term use is generally safe within NHS guidance (400 mg/day). Long-term use for constipation should be discussed with a healthcare professional as it’s not intended as a permanent solution.
Which is better for constipation — magnesium citrate or oxide?
Citrate is generally preferred for its higher bioavailability and better research base. Oxide works but requires more careful dosing, particularly in older adults or those with kidney conditions.
Final thoughts on magnesium for constipation
Magnesium is an effective natural option for constipation relief — particularly magnesium citrate. It’s not a long-term solution and should be used under medical guidance. Address the root cause (fibre, hydration, stress, medication) alongside any supplementation.
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