Electrolytes and GLP-1 dehydration

Semaglutide, tirzepatide, and related drugs slow how fast food and liquid leave the stomach. That can make plain water sit heavy during a workout. They also tend to blunt appetite — and thirst often rides the same signal. The result is athletes who are chronically under-hydrated but not particularly thirsty.

You cannot rely on thirst. You have to schedule fluids and electrolytes the same way you schedule calories.

A practical baseline for an active adult on a GLP-1 is about 3 liters of fluid per day, plus 500–1000ml per hour of training. If you are a heavy or salty sweater, or training in heat, you sit at the top of that range.

Sodium gets the most attention, but potassium and magnesium matter too — especially when you are sweating regularly and eating less food overall.

• Sodium: 500–1000mg per hour of training for most people. Heavy sweaters in heat may need more.
• Potassium: roughly 100–300mg per hour, or about 20% of your sodium loss.
• Magnesium: 50–100mg per hour. Many sports drink mixes leave this out, so check your label.

Plain water is fine for short, easy sessions. Once you are sweating for more than 45 minutes or it is hot, switch to an electrolyte drink mix. A good mix has sodium first, some potassium, and ideally a little magnesium. If carbonation or sweetness turns your stomach on the medication, look for low-sugar, non-carbonated options.

Headaches, muscle cramps, dark urine, elevated heart rate for the same effort, or dizziness when standing up can all point to under-replaced fluids or sodium. Do not push through these — fix the fueling and talk to your clinician if they persist.