Can GLP-1 medications cause fatigue or tiredness?

Yes, some people feel tired, especially in the first few weeks or after a dose increase on semaglutide or tirzepatide. Fatigue is usually mild and temporary, and is often related to eating far fewer calories, mild dehydration, or low protein rather than the medication itself. Ensuring adequate nutrition, hydration, and sleep usually helps; persistent fatigue should be discussed with your physician.

Why it happens

Reduced appetite can lead to eating too few calories or too little protein, which lowers energy. Dehydration and rapid changes in blood sugar can also contribute. These effects are most common early in treatment or after titrating up.

What helps

Don't under-eat — hit your protein target and eat enough overall, even when appetite is low. Stay hydrated, prioritize sleep, and rise slowly if you feel lightheaded. Contact your physician if fatigue is severe, persistent, or paired with other symptoms.

Medically reviewed by Dr. Michael Mimlitz, MD (NPI 1508891870), Chief Physician of GOAL.MD. Physician-supervised telehealth. More at goal.md/answers.