Weight Loss and GLP-1 Side Effects
Understanding GLP-1 Medications
GLP-1 receptor agonists (Ozempic, Wegovy, Mounjaro, and Zepbound) have transformed weight loss by mimicking glucagon-like peptide-1, a hormone naturally released after eating. These medications work by doing the following: they slow stomach emptying, which creates longer-lasting feelings of fullness; increase insulin secretion while decreasing glucagon (improving blood sugar control); and act directly on appetite centers in the brain to reduce hunger and food cravings. While highly effective—helping people lose 15% to 20% of their weight—they change your body's metabolism and digestion while you're on them. This explains why side effects are common, with most people having at least mild symptoms. Most side effects happen in the first few weeks of treatment or after you increase your dose. Keep in mind that these medications are meant to be used long-term use, and you're likely to regain weight if you stop taking them.
Nausea and Digestive Issues
Gastrointestinal symptoms are the most frequently reported side effects, affecting up to 44% of patients taking GLP-1 medications. Nausea is most common, followed by vomiting, diarrhea, constipation, and abdominal pain or discomfort. This is because GLP-1s slow down the movement of food through your stomach and gut. Most people find these symptoms are worst during the first 4-8 weeks of treatment or after you increase the dose. It can help if you eat smaller, more frequent meals rather than three large ones; avoid fatty, spicy, or high fiber foods during initial treatment; drink plenty of water; try ginger tea or peppermint for natural nausea relief; and take the medication at bedtime if daytime symptoms are bothering you. Some people may find relief from anti-nausea medications when they first start taking GLP-1s. If your symptoms are severe or last longer than 8 weeks, your doctor might temporarily reduce your dose before increasing it again more gradually.
Taste Changes and Food Aversions
Many GLP-1 users report that foods taste different or that they no longer like foods they previously enjoyed. They may no longer enjoy their favorite foods, or be extra sensitive to sweetness, metallic or bitter taste sensations, and they make strongly dislike certain foods and drinks —particularly sweets, fatty foods, and alcohol. Some people describe meat as suddenly tasting "gamey" or say that coffee tastes unpleasantly bitter. Many people view these changes in their tastes as beneficial "side effects" that help them eat less high-calorie food. For some people, these changes may last as long as they are taking GLP-1s. Try using herbs and spices to enhance flavor, trying new foods you previously disliked, focus on protein sources you can still tolerate, and stay flexible with your meal planning because your tastes may change from day to day.
Injection Site Reactions
GLP-1 medications are injected under the skin, and some people may have a reaction at the injection site, such as redness, itching, swelling, bruising, or occasionally small bumps under the skin. Most reactions are mild and get better within 3-5 days without treatment. Try rotating injection sites and avoid injecting into areas with bruises, scars, or stretch marks. Make sure the medication is at room temperature before injecting (cold medication increases discomfort); clean the site thoroughly with alcohol and allow it to dry completely; inject at a 90-degree angle with quick, confident motion; and avoid injecting into areas with scars, stretch marks, moles, or visible blood vessels. Using ice briefly before injection can reduce pain, while applying a cold compress afterward can minimize swelling. If you develop a rash, severe pain, warmth, or drainage at an injection site, tell your healthcare provider promptly as these may indicate infection.
Pancreas Problems
While rare, acute pancreatitis (an inflamed pancreas) represents one of the most serious potential complications of GLP-1 medication use, affecting approximately 0.1-0.2% of people. Seek medical attention immediately if you have severe, persistent abdominal pain that often radiates to the back, accompanied by nausea, vomiting, and sometimes fever. You're at higher risk if you have a history of pancreatitis, gallstones, heavy alcohol use, or very high triglyceride levels. Before starting treatment, your doctor should evaluate your baseline pancreatic enzyme levels through blood tests and continue monitoring periodically. You'll have to stop taking the GLP-1 if you have pancreatitis.
Muscle Loss
People lose both fat and muscle when on GLP-1s. Research suggests that up to 20-30% of total weight loss may come from muscle rather than fat—a problem since muscle is so important for your metabolism, long-term weight maintenance, and everyday life. You lose muscle mainly because GLP-1 medications reduce overall calorie intake, often dramatically, so you may not be getting enough protein. To minimize muscle loss while on these medications, get enough protein (approximately 100-150 grams for most adults); do resistance training 2-3 times weekly, focusing on major muscle groups; make sure you're getting enough nutrients, especially calcium and vitamin D for bone health; and consider working with a registered dietitian to develop a personalized nutrition plan. Some healthcare providers also recommend body composition analysis before and during treatment to monitor your muscle mass.
Gallbladder Complications
Rapid weight loss from GLP-1 medications increases the risk of gallbladder disease. The main problem is gallstones. These stones can cause intense pain, particularly after fatty meals. Call your health care provider right away if you have any of the following symptoms: Your skin or the whites of your eyes turning yellowish in color (also called jaundice); Fever; Pain in your upper stomach area; Stool (poop) that is clay-colored.
Hair Thinning
Hair thinning or increased shedding affects approximately 5-10% of patients on GLP-1 medications, typically beginning 3-6 months after starting treatment. You're more likely to see hair thinning rather than patchy baldness. This is a condition called telogen effluvium, where significant physiological stress—in this case, rapid weight loss and potential nutritional changes—pushes an unusually high percentage of hair follicles into their resting phase simultaneously. The good news is that this type of hair loss is almost always temporary, with regrowth typically beginning once weight stabilizes and you're getting better nutrition. To minimize hair thinning, make sure you get enough protein and iron, zinc, biotin, and vitamins A and D, which all support hair health; consider a multivitamin formulated for hair support; and avoid very low-calorie diets (under 1,000 calories daily) unless medically supervised. Gentle hair care practices also help: minimize heat styling, chemical treatments, and tight hairstyles; and handle wet hair carefully to avoid breakage. Most people see their hair start to grow again within 3-6 months after their weight stabilizes.
Mood Changes
Some people taking GLP-1s notice a change in their mood, such as depression, anxiety, or unusual irritability. These effects may result from hormonal shifts, changes to your diet, or other factors. Some people have a difficult time adjusting to the changes in their relationship with food, especially if they have a history of eating disorders. Some patients also say they can no longer tolerate alcohol or no longer want to drink. While rare, some people have reported suicidal thoughts. Let your healthcare provider know about any changes in your mental well-being. If you have an existing mental health condition, talk about the risks with your doctor before you start treatment.
Thyroid Concerns
GLP-1 medications carry a warning regarding thyroid C-cell tumors based on findings in animal studies, where these medications increased the incidence of thyroid cancer. While this effect has not been confirmed in humans, the FDA requires this warning out of an abundance of caution. Talk to your doctor if you have a personal or family history of thyroid cancer. During treatment, watch for symptoms that could indicate thyroid issues: difficulty swallowing, hoarseness or voice changes, shortness of breath, or a noticeable lump in the neck.
When to Seek Help
Contact your healthcare provider immediately for: severe, persistent abdominal pain, especially if it radiates to your back (possible pancreatitis); persistent vomiting or inability to keep fluids down for more than 24 hours (risk of dehydration); severe headache with vision changes (possible secondary effect on blood pressure); signs of allergic reaction like rash, itching, swelling of face/lips/tongue, or difficulty breathing (rare but serious); sudden, intense pain in the upper right abdomen, particularly after eating (possible gallbladder issue); unusual fatigue, weakness, or dizziness (potential hypoglycemia, especially if taking diabetes medications); yellowing of skin or eyes or dark urine (possible liver effects); persistent or severe depression, anxiety, or thoughts of self-harm (requires immediate evaluation); or any symptom that really bothers you. Don't stop taking your medication without talking to your doctor.