NZ GLP-1 hub · Supplements · 5 November 2026 · Official regulatory source
Magnesium: sleep, cramps and constipation, checked
General information, not advice. Supplements can interact with medicines. Talk to your doctor or pharmacist before starting one, especially if you take other medicines, are pregnant, or have a kidney or liver condition.
Why people take it
Magnesium helps regulate muscle and nerve function. People take it for sleep, muscle cramps and constipation.
Why it comes up with GLP-1 medicines
Eating less can mean less magnesium, which is found in nuts, seeds, legumes, wholegrains and leafy greens. Constipation is a common GLP-1 side effect, and some magnesium forms have a laxative effect.
What the evidence shows
Correcting a true deficiency is important. For sleep, trials in older adults are low quality, so they can't support firm conclusions. For cramps, a Cochrane review found magnesium is unlikely to give older adults a meaningful benefit. Magnesium is also a key ingredient in some laxatives.
What it doesn't show
A 2026 analysis of trials found a small fall in body weight, about 0.7 kg, but no significant change in BMI or body fat percentage.
Who should be careful
- →High intakes from supplements can cause diarrhoea, nausea and abdominal cramping, which can add to GLP-1 gut symptoms.
- →In healthy people the kidneys clear excess magnesium, so if you have kidney disease, talk to your doctor before taking it.
- →Magnesium may interact with some antibiotics (tetracyclines and quinolones) and osteoporosis medicines (oral bisphosphonates). Ask your pharmacist about timing.
- →The Australia–New Zealand upper limit for supplemental magnesium in adults is 350 mg a day; this limit applies to supplements, not food.
- →If constipation on a GLP-1 medicine is a problem, talk to your prescriber or pharmacist rather than self-treating.
Food first
Nuts, seeds, legumes, wholegrains and leafy greens.
Sources
- NIH Office of Dietary Supplements — Magnesium, health professional fact sheet
- Nutrient Reference Values for Australia and New Zealand — Magnesium
- Mah J, Pitre T — Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis (BMC Complementary Medicine and Therapies) · 2021
- Garrison SR et al. — Magnesium for skeletal muscle cramps (Cochrane Database of Systematic Reviews) · 2020
- NIH Office of Dietary Supplements — Magnesium, consumer fact sheet
- Mohammadi S et al. — Comprehensive effects of magnesium supplementation on cardiometabolic risk factors (Nutrients) · 2026
Review: Founder review via PR merge. General information only; no recommendations, brands, prices or product links; sources verified 5 Nov 2026.
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