CLINICAL PATIENT GUIDE · 2025

GLP-1 Agonists: Side Effects Explained & How to Make Them Go Away

Ozempic, Wegovy, Mounjaro, Zepbound & More — Everything Patients Need to Know Before, During, and After Treatment

By Dr. Mark G. Agresti, MD  ·  Board-Certified Psychiatrist  ·  Mark G. Agresti MD LLC  ·  DrMarkAgresti.com

OzempicWegovyMounjaroZepboundSaxendaVictozaRybelsus

CONTENTS

1. What Are GLP-1 Agonists?
2. GI Side Effects
3. Appetite & Eating Changes
4. Psychiatric & Mood Effects
5. Cardiovascular Effects
6. Metabolic & Endocrine Effects
7. Muscle & Joint Effects
8. Rare but Serious Risks
9. How to Treat Each Side Effect
10. Integrative Approaches
11. When to Call Your Doctor

GLP-1 receptor agonists are among the most exciting — and most misunderstood — medications of the decade. Millions of Americans are now taking Ozempic, Wegovy, Mounjaro, or Zepbound for diabetes or weight loss, often without a full picture of what these drugs can do to the body and mind. As a psychiatrist who takes an integrative approach to patient care, I see the downstream effects of these medications regularly — and I want my patients to be fully informed.

This comprehensive guide walks through every major side effect category, explains why these effects happen, and most importantly — provides evidence-based strategies to manage or eliminate them so you can stay on your treatment without suffering through it.

SECTION 1

What Are GLP-1 Agonists — and Why Are So Many People Taking Them?

GLP-1 stands for glucagon-like peptide-1, a hormone naturally released by the gut after eating. It signals the pancreas to release insulin, tells the brain you’re full, slows gastric emptying, and suppresses glucagon (which raises blood sugar). GLP-1 agonists are synthetic drugs that mimic — and dramatically amplify — this hormone’s effects.

Ozempic

Semaglutide (injectable)

Type 2 diabetes management; off-label weight loss

GLP-1 AGONIST

Wegovy

Semaglutide (higher dose, injectable)

FDA-approved chronic weight management

GLP-1 AGONIST

Mounjaro

Tirzepatide (injectable)

Type 2 diabetes; dual GIP/GLP-1 mechanism

DUAL GIP/GLP-1

Zepbound

Tirzepatide (same drug, weight loss label)

FDA-approved for obesity & weight-related conditions

DUAL GIP/GLP-1

Saxenda

Liraglutide (daily injectable)

Chronic weight management; pediatric obesity

GLP-1 AGONIST

Victoza

Liraglutide (diabetes dose)

Type 2 diabetes; cardiovascular risk reduction

GLP-1 AGONIST

Rybelsus

Semaglutide (oral tablet)

Type 2 diabetes; first oral GLP-1 option

GLP-1 AGONIST

Mounjaro and Zepbound are technically dual agonists — they activate both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors, which is why they tend to produce greater weight loss than pure GLP-1 drugs. But this also means a somewhat different — and often more intense — side effect profile.

SECTION 2

Gastrointestinal Side Effects: The Most Common Complaints

GI side effects are the most frequently reported issues with all GLP-1 medications. They occur because GLP-1 receptors are densely expressed throughout the gastrointestinal tract, and activating them slows the movement of food through your digestive system.

🤢Nausea — Affects 30–50% of patients, especially in the first 4–8 weeks

Nausea is the hallmark GLP-1 side effect. It’s caused primarily by slowed gastric emptying and direct activation of nausea receptors in the brainstem. It typically peaks in the first few weeks after a dose increase and tends to improve significantly over time as the body adapts.

• Timing: Usually peaks 6–12 hours after injection
• Pattern: Often worst in the morning or after eating
• Severity: Mild queasiness to severe nausea requiring temporary dose reduction
• Timeline: Most patients see significant improvement by weeks 8–12

🚽Vomiting, Diarrhea & Constipation

GLP-1 medications can disrupt the normal rhythm of gut motility — sometimes speeding it up (causing diarrhea and loose stools), sometimes slowing it dramatically (causing constipation). Some patients cycle between both.

• Vomiting: Occurs in 10–25% of patients; usually short-lived and linked to dose escalations
• Diarrhea: Reported in 15–30%; watery stools, often without cramping
• Constipation: Affects up to 20% of patients; more common on semaglutide than tirzepatide
• Gastroparesis-like symptoms: Feeling uncomfortably full hours after eating; bloating; belching

🫄Bloating, Belching & GERD

Because GLP-1 drugs dramatically slow how quickly food leaves your stomach (gastric emptying), food sits longer, producing gas, pressure, and acid reflux. Pre-existing GERD can worsen significantly on these medications.

• Excess belching is common, especially after meals
• GERD and heartburn flares are reported in 5–15% of patients
• Abdominal bloating, particularly in the upper abdomen
• A sense of early and prolonged fullness (which is partly the mechanism of action, not purely a side effect)

SECTION 3

Appetite Suppression & Food Aversions

One of the most dramatic effects of GLP-1 medications is a profound reduction in appetite — and for many patients, this goes far beyond simply “not feeling hungry.” These changes occur because GLP-1 receptors are found in the hypothalamus and reward centers of the brain, directly modulating hunger signals and food motivation.

🍽️Dramatic Loss of Appetite & Food Noise Reduction

Many patients describe a phenomenon sometimes called “food noise” disappearing — the constant mental preoccupation with food, what to eat next, or cravings. While this is a desired therapeutic effect, it can become problematic when appetite suppression is so extreme that patients are not eating enough.

• Some patients eat only 400–700 calories per day without feeling hungry
• Protein and caloric deficits can accelerate muscle loss alongside fat loss
• Nutrient deficiencies (B12, iron, zinc) are underrecognized risks
• Fatigue and weakness from inadequate intake are common but often misattributed

🥩Food Aversions & Sensory Changes

A surprisingly common but underreported effect is the development of specific food aversions — particularly to high-fat, fried, or previously enjoyed foods. Some patients report that foods they loved before now smell or taste repulsive. Others develop new aversions to alcohol, caffeine, or red meat.

• Aversions to greasy or fried food are among the most common
• Many patients spontaneously reduce alcohol consumption (studied in clinical trials)
• Taste changes — foods taste too sweet, too fatty, or “off”
• Social eating challenges: difficulty eating at restaurants or with family

SECTION 4

Psychiatric & Mood-Related Side Effects

As a psychiatrist, this is an area I follow closely and discuss with every patient considering GLP-1 therapy. These medications act in brain regions involved in reward, motivation, mood, and impulse control — which means psychiatric effects are real and require monitoring.

A NOTE FROM DR. AGRESTI

At Mark G. Agresti MD LLC, I work with many patients who are on GLP-1 medications prescribed by their internist or endocrinologist. The psychiatric and mood-related side effects of these drugs are often overlooked in primary care settings. If you are experiencing depression, anxiety, or suicidal thoughts while on a GLP-1 medication, please contact my office or seek care immediately. Visit DrMarkAgresti.com to schedule a consultation.

😔Depression, Anxiety & Mood Changes

The FDA has received reports of suicidal ideation and self-injurious behavior in patients taking GLP-1 agonists. While a causal link has not been firmly established and the FDA concluded in 2024 that the evidence does not confirm causality, mood changes deserve serious attention — particularly in patients with pre-existing psychiatric conditions.

• Depression: Some patients report worsening depressive symptoms, particularly in the first 2–3 months
• Anxiety: Heightened anxiety, especially food-related anxiety in patients with eating disorder history
• Anhedonia: Loss of pleasure in food can extend to broader loss of interest in activities; this overlaps significantly with depression symptoms
• Irritability & emotional blunting: Some patients describe feeling “flat” or emotionally muted

⚠️ IMPORTANT SAFETY NOTE

If you or someone you know experiences suicidal thoughts, self-harm urges, or severe psychiatric symptoms while taking a GLP-1 medication, stop the medication and seek immediate medical care. Call 988 (Suicide & Crisis Lifeline) or go to your nearest emergency room.

😴Fatigue, Brain Fog & Sleep Disruption

Fatigue is among the top 5 reported side effects across all GLP-1 clinical trials. It can stem from multiple converging causes — inadequate caloric intake, disrupted sleep, dehydration from GI symptoms, or direct neurological effects of the medication.

• Fatigue: Often most pronounced in the first 4–8 weeks and after dose escalations
• Cognitive sluggishness: Difficulty concentrating or “thinking through fog” — may be related to caloric restriction
• Sleep changes: Vivid dreams, disrupted sleep, or excessive daytime sleepiness reported by a subset of patients
• Low motivation: Overlaps with depression; requires clinical differentiation

SECTION 5

Cardiovascular & Autonomic Side Effects

❤️Heart Rate Increases

GLP-1 receptors are expressed on cardiac tissue. All GLP-1 agonists cause a modest but consistent increase in resting heart rate — typically 2–5 beats per minute, though increases of 10–20 bpm have been reported in some patients.

• Usually asymptomatic; detected on routine monitoring
• Some patients experience palpitations, particularly at higher doses
• Heart rate tends to normalize over time or with dose reduction
• Despite the heart rate increase, GLP-1 drugs have demonstrated cardiovascular benefit in clinical trials (LEADER, SUSTAIN-6, SURMOUNT-MMO) — reduced heart attacks and strokes

💧Dehydration & Blood Pressure Changes

GI side effects (nausea, vomiting, diarrhea) frequently lead to inadequate fluid intake and frank dehydration. Separately, GLP-1 drugs independently cause modest reductions in blood pressure — beneficial in most patients, but potentially problematic in those already on antihypertensives.

• Lightheadedness, dizziness, and orthostatic hypotension can occur
• Patients on blood pressure medications should have their dosing reassessed
• Kidney function (eGFR, creatinine) should be monitored, as dehydration combined with certain medications (NSAIDs, ACE inhibitors, diuretics) can cause acute kidney injury

SECTION 6

Metabolic & Endocrine Side Effects

🩸Hypoglycemia (Low Blood Sugar)

When used alone, GLP-1 drugs have a very low risk of hypoglycemia because they are glucose-dependent — they only stimulate insulin when blood sugar is elevated. However, when combined with sulfonylureas (like glipizide, glimepiride) or insulin, the hypoglycemia risk increases substantially.

• Symptoms: sweating, shakiness, confusion, rapid heartbeat
• Dose reduction of the concurrent medication is usually required
• Patients should know to carry fast-acting glucose (juice, glucose tablets)

💪Muscle Loss (Sarcopenia) — An Underappreciated Risk

Clinical trials have shown that 25–40% of the weight lost on GLP-1 medications is lean mass (muscle), not fat. In older adults, this can accelerate sarcopenia — age-related muscle loss — with serious long-term consequences for strength, mobility, bone density, and metabolic health.

• Most at risk: Adults over 60, those eating very low protein, sedentary individuals
• Muscle loss is not always visible — patients can look thinner while becoming functionally weaker
• Resistance training and adequate protein intake (1.2–1.6g per kg body weight) are essential protective strategies
• Some physicians are now co-prescribing creatine supplementation to help preserve lean mass

🦴Hair Loss (Telogen Effluvium)

Hair loss is one of the most distressing side effects reported by GLP-1 patients, though it is not caused directly by the drug itself. Rather, it is caused by rapid weight loss and caloric restriction — which trigger a physiological stress response called telogen effluvium, where hair follicles prematurely shift into a resting/shedding phase.

• Usually begins 2–4 months after significant weight loss starts
• Typically temporary; hair regrows when nutrition stabilizes
• Higher protein intake, biotin, zinc, and iron repletion may help
• Not reported at the drug mechanism level; dietary adequacy is the solution

SECTION 7

Musculoskeletal & Injection-Site Effects

💉Injection Site Reactions & Pain

Redness, bruising, itching, and nodule formation at the injection site affect a minority of patients but can become a persistent nuisance. Rotating injection sites (abdomen, thigh, upper arm) and allowing the pen to reach room temperature before injecting significantly reduces reactions.

• Let the medication sit at room temperature for 30 minutes before injecting
• Rotate among three areas: abdomen, outer thigh, upper arm
• Avoid re-injecting within 2 inches of a previous site for at least 2 weeks
• Use a new needle for each injection

🦵Joint Pain & “GLP-1 Arthralgia”

Joint pain has been reported in clinical trials, though it is less common than GI effects. Some patients also report generalized muscle aches and weakness, particularly in the early weeks of therapy. This can be related to the muscle-loss effect described above.

• Joint pain (arthralgia) reported in 5–10% of patients in some trials
• Back pain is among the more common musculoskeletal complaints
• Weight loss itself improves joint pain long-term, even if short-term aching occurs

SECTION 8

Rare but Serious Risks

While uncommon, the following serious adverse events carry FDA black box warnings or significant clinical concern and should be discussed with every patient before initiating therapy.

SECTION 9

How to Treat GLP-1 Side Effects: Evidence-Based Strategies

The good news: the vast majority of GLP-1 side effects are manageable. Most improve significantly with time, dietary adjustments, and when needed — short-term medical support. Here is a systematic guide to treating each major category.

Treating Nausea

Treating Constipation

Treating Diarrhea & Loose Stools

Treating Fatigue & Muscle Loss

Addressing Psychiatric & Mood Side Effects

SECTION 10

Integrative Approaches to GLP-1 Support

At Mark G. Agresti MD LLC, I approach GLP-1 therapy as one piece of a larger puzzle. Patients who do best on these medications are those who use the dramatic appetite suppression as an opportunity to build better habits — not simply eat less of everything. Here are the integrative strategies I recommend most consistently:

🥗Nutrition Strategy: Nutrient-Dense, Protein-Forward Eating

When appetite is profoundly reduced, every calorie must count. I recommend patients work with a registered dietitian who understands GLP-1 pharmacology to ensure micronutrient adequacy and protein sufficiency.

• Prioritize protein at every meal: eggs, Greek yogurt, lean meat, legumes, cottage cheese
• Keep fast food and ultra-processed foods minimal — they are more likely to trigger nausea
• Eat foods rich in potassium, magnesium, and B vitamins to counter GI losses
• Consider a comprehensive multivitamin and targeted supplementation (B12, D3, iron, zinc)

🧘Mind-Body & Stress Reduction

Stress significantly worsens GI motility issues and amplifies nausea on GLP-1 medications. The gut-brain axis is directly relevant here. Patients who actively manage stress tend to have a smoother experience on these medications.

• Mindfulness-based stress reduction (MBSR) — 8-week programs are widely available online
• Diaphragmatic breathing: activates the vagus nerve, which calms gut motility
• Yoga and gentle movement: improves gut function and mood
• Journaling: helps track symptom patterns and emotional triggers around eating

🏋️Exercise: The Non-Negotiable Companion

Exercise is not optional when taking GLP-1 medications — it is essential. Without resistance training, patients risk losing significant lean muscle mass alongside fat. Clinical guidelines increasingly recommend that GLP-1 therapy be paired with structured exercise.

• Resistance training at least 2–3 times per week: squats, deadlifts, rows, presses
• 30+ minutes of moderate aerobic activity most days
• Walking after meals reduces postprandial glucose spikes and improves GI motility
• Work with a personal trainer if you are new to exercise — form matters for injury prevention

SECTION 11

When to Call Your Doctor — Or Seek Emergency Care

⚠️ GO TO THE ER IMMEDIATELY IF YOU EXPERIENCE:

Severe upper abdominal pain (possible pancreatitis) · Neck mass or difficulty swallowing (possible thyroid issue) · Signs of severe dehydration (inability to keep fluids down for 24+ hours) · Suicidal thoughts or self-harm urges · Chest pain or irregular heartbeat · Signs of intestinal obstruction (severe distension, unable to pass gas)

CALL YOUR PRESCRIBER IF YOU NOTICE:

Persistent nausea lasting more than 8 weeks · Vision changes · New or worsening depression or anxiety · Hair loss that is severe or accelerating · Significant fatigue and weakness · Blood sugar readings that are consistently too low · Inability to maintain adequate food and fluid intake

Navigating GLP-1 Therapy? Let’s Talk.

Dr. Mark G. Agresti offers integrative psychiatric care for patients across Florida — including those managing the mental and emotional dimensions of GLP-1 therapy.

SCHEDULE AT DRMARKAGRESTI.COM

In-person in Palm Beach · Telemedicine statewide in Florida www.drmarkagresti.com · Mark G. Agresti MD LLC · 44 Cocoanut Row, Suite M202, Palm Beach, FL