Muscle cramps and electrolytes

What members report

Cramp in the calves at two in the morning. A foot that seizes when you point your toes in bed. Twitching in an eyelid or a thumb for a fortnight. Legs that feel heavy on a staircase they used to manage.

None of this appears as a notable finding in the pivotal trials. Muscle spasms turn up in adverse-event tables at low rates across this drug class and were not a safety signal in STEP 1 (Wilding, NEJM, 2021) or SURMOUNT-1 (Jastreboff, NEJM, 2022). Meanwhile it comes up steadily in Ren’s circles, particularly among members who lift and members over sixty.

Ren’s position, which we like: cramps are usually a signal about fluid, minerals, intake or unaccustomed load, and occasionally a signal about something that needs a blood test. The useful work is telling the two apart rather than reaching for a supplement.

The plausible explanations

In rough order of how often members trace it back to them.

• Being dry. Reduced thirst plus reduced intake plus a hot week. The commonest story by far.
• Sodium. Eating much less food usually means eating much less salt, and members who had had a spell of vomiting or diarrhoea are further behind again. This is the mineral most often overlooked because most people assume the answer is potassium or magnesium.
• Magnesium and potassium. Plausible, particularly after gastrointestinal losses, and genuinely worth a blood test rather than a guess — both can be measured.
• Not enough protein while losing weight. Muscle under-fed and under-loaded is muscle that complains. The protein guide covers the practical side.
• Unaccustomed load. Members who start walking or lifting after years off will cramp, and that is training rather than pathology.
• Medicines. Diuretics, some blood pressure medicines, statins and others are all associated with cramps or muscle symptoms. A pharmacist can review the list.
• Something separate. Thyroid problems, low vitamin D, poorly controlled glucose, kidney issues, and circulation problems in the legs all cause muscle symptoms and none of them stop because you started a new medicine.

The electrolyte conversation, honestly

This is where the internet gets loud and where we are going to be dull on purpose.

There is no established electrolyte protocol for people on GLP-1 medicines. No trial has tested supplementation for cramps in this population. The elaborate mineral regimens circulating in online groups are extrapolated from endurance sport and from very-low-intake dieting, and they are not neutral: potassium supplements can be genuinely dangerous in people with reduced kidney function or on certain blood pressure medicines, and sodium loading is not appropriate for everyone with high blood pressure or heart failure.

What is reasonable, and what members mostly do: cover fluid properly, do not let salt intake collapse to nothing, get food-based magnesium and potassium where you can, and if cramps are persistent, ask for the blood test that measures the thing rather than supplementing at a guess. FLOW (Perkovic, NEJM, 2024) is a reminder of how relevant kidney function is in this population — and kidney function is exactly what determines whether a mineral supplement is harmless or not.

Oral rehydration sachets from a pharmacy are designed for the specific job of replacing fluid and salts after gastrointestinal losses, and are a better answer than most things sold for athletes. Hydration and electrolytes goes further into all of this.

What has helped in the moment

Member practice, unglamorous, no trial evidence.

• Stretch into it rather than away from it. For a calf cramp, straighten the knee and pull the toes towards you. For a foot, stand up and press the sole flat on the floor.
• Warmth afterwards. A hot water bottle or a warm shower for the ache that follows.
• Stretching calves before bed. Modest evidence in the general night-cramp literature and reported to help by a good number of members.
• Drinking something salty in the evening on days you have not eaten much. Broth is the version most people manage.
• Loosening the bedclothes at the foot of the bed. Sounds absurd, repeatedly reported to work for people whose cramps come with pointed toes.
• Keeping the legs loaded. Ren’s standing point: muscle that is used regularly cramps less than muscle that has been resting for a fortnight.

Quinine, which older relatives will suggest, is not recommended for cramps in most countries any more because of the risks. Do not take somebody’s leftovers.

The strength question underneath

Cramps often arrive alongside the thing Ren actually worries about, which is losing strength during a phase of rapid change.

Any substantial weight loss includes some loss of lean tissue. That is not specific to these medicines and it is well established in the general weight-loss literature. The mitigations are equally well established and fit on a postcard: keep enough protein coming in, and keep loading your muscles — particularly through the weeks when you feel worst, which is exactly when people stop.

What the GLP-1 trials do not give us is a specific answer about how much protein or what kind of training works best on these drugs. So we are honest about the provenance: the resistance-training and protein advice is imported from a wider literature and it is the best available reasoning rather than a finding about this drug class. Keeping your strength through a loss phase and protein and strength, the basics are the two guides that go further, and eight minutes and a chair is for the fortnights when the good intentions have collapsed.

Lena in Munich, who came to this a barbell first and everything else second, says the thing that kept her strong was not a clever programme but refusing to skip her two sessions in the worst month. Two sessions, badly, beats none.

When a muscle symptom is not a cramp

Short list, because muscle pain has a couple of serious causes and they are worth recognising.

• Severe, widespread muscle pain with weakness, particularly with dark or cola-coloured urine. Same-day assessment. That combination can indicate muscle breakdown, which affects the kidneys.
• New muscle pain or weakness after starting or increasing a statin. Contact your clinician rather than stopping on your own.
• Weakness rather than cramp — difficulty rising from a chair or climbing stairs that is new and progressing. That deserves proper assessment, not a supplement.
• Cramping in the calf on walking that stops when you rest, reliably, at the same distance. That pattern is worth investigating for circulation.
• One calf, swollen, hot, tender and painful. Urgent — that is the picture of a clot, not a cramp.
• Cramps with palpitations, confusion, or profound weakness after days of vomiting or diarrhoea. Same-day; that is the electrolyte situation that needs measuring rather than guessing.

The full red-flag list is here, and the general rule this community runs on applies: if the symptom is frightening you, that is reason enough to have it looked at.