GLP-1 Muscle Cramps: Why Your Legs Cramp on Ozempic (2026)

Short answer

GLP-1s don't cause cramps — they cause the electrolyte deficit that does.Reduced food intake + GI losses quietly drain magnesium, potassium, and sodium, and muscles low on those minerals cramp — classically the midnight calf cramp that makes you sit bolt upright. It's the same mechanism athletes get cramping in hard training: working muscles, thin electrolytes. The fix is repletion, not waiting for the drug to 'wear off'.

The electrolyte math

Three minerals run your muscle's contract-relax cycle: magnesium (the relaxation switch — low levels let fibers hold a partial contraction that twitches into cramp), potassium (membrane stability — low levels make muscles hyperexcitable), and sodium (fluid and nerve signaling — low levels cause cramps plus that foggy, weak feeling). On a GLP-1 you lose all three through reduced intake and possible GI losses, while your body still demands them 24/7.

Why nights specifically: sleep lowers your physiological set-point for muscle relaxation — a borderline-depleted system that's functional at noon hits the cramp threshold at 3am.

The mineral fix

• Magnesium glycinate or citrate, 200-400mg at night. Best absorbed forms; skip oxide (poor uptake, laxative at dose) unless you also want help with constipation — in which case, pick your trade-off.
• Food potassium. Supplements are capped at 99mg — get it from avocado, potato, coconut water, yogurt. A daily serving covers the gap.
• Don't fear the salt. On low food intake, sodium deficiency is real — cramps that resist magnesium are usually a salt problem. A light electrolyte mix or salted water handles it.
• Water through the day. Concentrated, dehydrated muscle tissue cramps easier — the same 2-3L target as every other GLP-1 side effect.

When cramps aren't just electrolytes

• Dark, cola-colored urine or severe muscle weakness — possible rhabdomyolysis, urgent
• One-sided leg cramp + swelling + warmth — possible clot, urgent
• Cramps persisting weeks despite repletion — check thyroid and nerve function
• Severe dehydration signs alongside — the cramps are telling you something bigger

One more note: if you're doing resistance training (which you should, for muscle preservation), your electrolyte demand is higher — treat cramps as the deficit making itself visible, not a reason to stop lifting.

Related guides

• Preventing Muscle Loss on GLP-1
• Dizzy on Ozempic? 7 Causes & Fixes
• GLP-1 and Dehydration
• GLP-1 and B12 Deficiency
• GLP-1 Supplements Guide
• GLP-1 and Constipation Fixes