GLP-1 medications like Ozempic, Mounjaro, Wegovy, and Zepbound are remarkably effective — but they come with side effects that most users experience at some point, especially during dose increases.

Tracking these side effects isn't just useful. It's one of the most important things you can do to get better care from your doctor.

Common GLP-1 Side Effects

Most side effects are gastrointestinal and tend to improve over time. Here's what to watch for.

Frequently Reported

Nausea — The most common side effect across all GLP-1s. Usually worst during the first 1–2 weeks of a new dose and improves with time.
Constipation — GLP-1s slow gastric emptying, which can affect bowel regularity.
Diarrhea — Some people experience the opposite. It can alternate with constipation.
Reduced appetite — This is actually the intended effect, but it can feel intense at first.
Fatigue — Common in the first few days after a dose increase.

Less Common but Worth Tracking

Headaches — Usually mild and temporary.
Dizziness — Can occur, especially if you're not eating or drinking enough.
Injection site reactions — Redness, itching, or swelling at the injection site.
Acid reflux / heartburn — Slower gastric emptying can worsen reflux.
Hair thinning — Reported by some users, likely related to rapid weight loss rather than the medication itself.

How to Track Side Effects Effectively

Rate Severity Consistently

Use a simple scale every time you log a side effect:

Mild — Noticeable but doesn't affect your daily activities
Moderate — Affects your day but you can still function
Severe — Significantly impacts your ability to do normal activities

Consistency is key. What you call "moderate" on day 1 should mean the same thing on day 30.

Note the Timing

Side effects often follow predictable patterns:

Post-injection surge: Some people feel nauseous 12–24 hours after injecting
Dose-increase window: Side effects typically flare for 2–5 days after moving to a higher dose
Food triggers: Certain foods (greasy, fried, large portions) can amplify GI side effects

Tracking when side effects occur relative to your injection helps identify these patterns.

Track Duration

Did the nausea last 2 hours or 2 days? This distinction matters enormously to your prescriber.

A brief wave of nausea is very different from all-day nausea that prevents eating.

When to Contact Your Doctor

Most GLP-1 side effects are manageable, but some warrant a call to your healthcare provider:

Severe or persistent nausea/vomiting that prevents you from eating or drinking for more than 24 hours
Signs of pancreatitis — severe abdominal pain that radiates to your back
Signs of low blood sugar — shakiness, sweating, confusion (especially if you're also on insulin or sulfonylureas)
Allergic reactions — difficulty breathing, severe rash, swelling
Any side effect rated "severe" that doesn't improve within a few days

Why Your Doctor Needs This Data

When your doctor asks "how are you tolerating the medication?" the quality of your answer directly impacts their treatment decisions.

Without tracking:

"I had some nausea. It was okay, I guess."

With tracking:

"I had moderate nausea for 3 days after increasing to 1 mg. It peaked on day 2 and resolved by day 4. I also noticed mild constipation that improved with more water. No other side effects."

The second response gives your doctor the information they need to decide whether your current dose is appropriate, whether to slow your titration, or whether to add supportive medications.

Managing Common Side Effects

A few practical strategies that many GLP-1 users find helpful:

For nausea: Eat bland, small meals. Ginger tea or ginger candies can help. Avoid lying down right after eating.
For constipation: Increase water and fiber intake. Gentle movement like walking can help.
For fatigue: Stay hydrated, get adequate sleep, and don't skip meals entirely even if your appetite is reduced.
For injection site reactions: Rotate sites consistently (abdomen, thigh, upper arm) and let the pen warm to room temperature before injecting.

Track It All In One Place

Gilly lets you log side effects with severity ratings alongside your injection and weight data.

When patterns emerge — like nausea always peaking on day 2 after an injection — you'll see it clearly in your history. At your next appointment, generate a comprehensive PDF report that gives your doctor the full picture.

Free to download. Start tracking today from the App Store.