Side Effect Guide

GLP-1 Side Effects

Understand every potential side effect, how to manage them, and when to seek medical attention. 25 side effects grouped by category and severity.

Very Common Common Uncommon Rare

Gastrointestinal

Side effects affecting the digestive system

Very Common 40-50% of patients

Nausea

Feeling of sickness with an inclination to vomit, especially common during dose titration periods

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Common 5-15% of patients

Vomiting

Forceful expulsion of stomach contents, often occurring alongside nausea during dose escalation

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Very Common 15-30% of patients

Diarrhea

Frequent loose or watery stools, often occurring early in treatment or after dose increases

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Very Common 15-25% of patients

Constipation

Infrequent or difficult bowel movements, often with hard or dry stools

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Common 5-20% of patients

Abdominal Pain / Stomach Cramps

Pain, cramping, or discomfort in the stomach or abdominal area, ranging from mild to moderate

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Common 10-20% of patients

Bloating / Gas

Feeling of fullness, tightness, or swelling in the abdomen, often accompanied by increased gas or flatulence

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Common 5-15% of patients

Acid Reflux / GERD

Heartburn, acid taste in mouth, or burning sensation in the chest caused by stomach acid flowing back into the esophagus

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Uncommon 1-5% of patients (severe form)

Gastroparesis (Delayed Gastric Emptying)

Significantly delayed emptying of the stomach, causing prolonged fullness, nausea, and in severe cases, vomiting of undigested food hours after eating

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Common 10-20% of patients

Sulfur Burps

Burps that taste and smell like rotten eggs (hydrogen sulfide), sometimes accompanied by nausea or an upset stomach

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Metabolic

Side effects related to metabolism and blood chemistry

Uncommon 1-5% when used alone; higher when combined with insulin or sulfonylureas

Low Blood Sugar (Hypoglycemia)

Blood sugar dropping below normal levels, causing shakiness, sweating, confusion, rapid heartbeat, and in severe cases, loss of consciousness

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Very Common 30-50% of patients report significant appetite loss

Decreased Appetite (Beyond Intended)

Extreme reduction in appetite or food aversion that goes beyond the therapeutic intent, sometimes making it difficult to eat enough to meet basic nutritional needs

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Common 10-20% of patients may experience some degree of dehydration

Dehydration

Insufficient fluid levels in the body, caused by reduced fluid intake from appetite suppression combined with fluid losses from GI side effects

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Cosmetic / Aesthetic

Visible changes to appearance

Uncommon 3-6% of patients

Hair Loss / Thinning

Diffuse hair thinning or increased hair shedding, typically noticed several months after starting treatment

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Common Noticeable in most patients with significant weight loss (>15% body weight)

"Ozempic Face" (Facial Volume Loss)

Loss of facial fat and volume leading to a gaunt, hollow, or aged appearance — sagging skin, prominent cheekbones, under-eye hollows, and deeper nasolabial folds

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Neurological

Side effects affecting the nervous system

Common 10-15% of patients

Headache

Mild to moderate headaches, particularly during the early weeks of treatment

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Common 5-15% of patients

Fatigue / Tiredness

Persistent tiredness, low energy, or feeling of exhaustion that may affect daily activities

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Common 5-10% of patients

Dizziness

Lightheadedness, unsteadiness, or a feeling that the room is spinning, especially when standing up quickly

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Uncommon 2-5% of patients

Changes in Taste

Altered taste perception (dysgeusia) — foods may taste metallic, bitter, bland, or different than usual

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Uncommon 1-5% of patients

Depression / Mood Changes

Changes in mood including depression, anxiety, irritability, or emotional flatness, which may be new or a worsening of pre-existing conditions

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Musculoskeletal

Side effects affecting muscles and bones

Common Up to 40% of weight lost may be lean mass without intervention

Muscle Loss / Sarcopenia

Loss of muscle mass alongside fat loss during GLP-1-mediated weight loss, potentially leading to reduced strength, metabolic rate, and functional capacity

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Injection-Related

Side effects at or near the injection site

Common 5-10% of patients

Injection Site Reactions

Redness, swelling, itching, pain, or bruising at the site where the medication is injected

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Serious / Rare

Potentially serious side effects requiring medical attention

Uncommon 1-3% of patients

Gallbladder Issues / Gallstones

Formation of gallstones (cholelithiasis) or inflammation of the gallbladder (cholecystitis), causing pain in the upper right abdomen

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Rare 0.1-0.4% of patients

Pancreatitis

Inflammation of the pancreas causing severe abdominal pain that radiates to the back, requiring immediate medical attention

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Rare 0.1-0.5% of patients (acute kidney injury)

Kidney Issues

Kidney function impairment, including acute kidney injury (AKI), primarily caused by severe dehydration from GI side effects

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Rare Observed in animal studies; human incidence not established (FDA black box warning)

Thyroid Concerns

Potential risk of thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), based on findings in rodent studies. Carries an FDA black box warning.

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