GLP-1 Side Effects: What Research Reports and How to Track Them

If you have started a GLP-1 medication like semaglutide or tirzepatide, you have probably been told to "keep an eye on side effects." That is good advice, but it is vague. What should you actually watch for, and how do you keep notes that are useful when you talk to your provider?

This guide covers what the large clinical trials and official drug information report about GLP-1 side effects, and then walks through a simple way to log them. It is not a guide to what is normal for you. Only your licensed healthcare provider can judge that.

What the research reports about GLP-1 side effects

The best evidence we have comes from big randomized trials and the official patient information for each medication. Here is what they say, in plain terms.

Semaglutide

In the STEP 1 trial published in the New England Journal of Medicine, the most commonly reported side effects with semaglutide were gastrointestinal, such as nausea and diarrhea. The authors describe them as typically transient and mild to moderate, and say they subsided with time. More people in the semaglutide group than in the placebo group stopped treatment because of gastrointestinal events (4.5% compared with 0.8%).

Tirzepatide

The SURMOUNT-1 trial of tirzepatide found a similar pattern. The most common adverse events were gastrointestinal, most were mild to moderate, and they occurred mainly during dose escalation. That last detail matters for tracking, and we will come back to it.

What the official patient information lists

The U.S. National Library of Medicine keeps plain-language drug pages. The MedlinePlus page for semaglutide injection lists nausea, vomiting, diarrhea, stomach pain, constipation, heartburn and burping, among others, and tells readers to contact their doctor if any are severe or do not go away. It also lists more serious symptoms that call for immediate medical attention. The tirzepatide page has a comparable list.

The takeaway is simple. Stomach-related effects are the most commonly reported, they are often described as easing over time in trials, and some symptoms are serious enough that they should never wait for your next appointment. Your provider is the one who decides which is which for you.

Why a GLP-1 tracker helps with side effects

Memory is a poor record. A week after a rough day, most people remember that they "felt bad for a while" but not when it started, how strong it was, or what else was going on. A provider can do much more with specifics.

A GLP-1 tracker, whether it is a notebook, a spreadsheet or a GLP-1 tracker app, gives you three things memory cannot:

1. Timing. When did the symptom start relative to your dose?
2. Pattern. Does it show up after every dose, or only after a change?
3. Trend. Is it getting milder, staying the same or getting worse over weeks?

Remember the SURMOUNT-1 finding that side effects showed up mainly during dose escalation. If your log shows symptoms clustering right after a step up in your schedule, that is exactly the kind of pattern worth showing your provider. You do not need to interpret it yourself. You just need to have it written down.

What to record each time

Keep each entry short. A log you actually keep beats a detailed one you abandon after a week.

The basics

• Date and time of the symptom
• Date and time of your last dose, and which step of your provider's schedule you are on
• What you noticed, in your own words (for example, "queasy after lunch")
• Severity, on a simple scale like mild, moderate or severe
• How long it lasted

Helpful context

• What and how much you ate that day, roughly
• How much water you drank
• Sleep, stress or illness that might be relevant
• Anything you did that seemed to help or make it worse

Avoid diagnosing in your notes. Write "stomach pain, moderate, lasted two hours" rather than "probably gallbladder." Describing is your job. Interpreting is your provider's.

A simple severity scale you can use

Consistency matters more than precision. Pick a scale and stick with it so your entries are comparable week to week.

• Mild: you noticed it, but it did not change your day.
• Moderate: it changed what you ate or did, but you got through the day.
• Severe: it stopped you from normal activities.

If something feels severe, or matches the serious symptoms on the official drug information, contact your provider or seek urgent care right away. A log is for spotting patterns over time. It is not a reason to wait.

Reading the trend with your provider

After a few weeks, your log turns into something useful: a timeline. Before an appointment, take five minutes to look it over and note:

• How many days you logged a symptom this month compared with last month
• Whether symptoms cluster in the first few days after a dose
• Whether anything changed after a step in your titration schedule
• Any entry marked severe, with the date

Bring those points, plus the log itself, to your visit. Your provider can then decide what, if anything, should change. Never adjust your dose or schedule on your own based on what your log seems to show.

Common mistakes when tracking GLP-1 side effects

• Only logging bad days. Write down good days too, even with a quick "no symptoms." Otherwise your log looks worse than reality.
• Logging symptoms without dose times. Without the dose time, there is no way to see timing patterns.
• Changing the scale halfway. If "moderate" meant something different in month one and month two, the trend is meaningless.
• Relying on memory the night before an appointment. Log on the day, even if it is one line.
• Leaving out weight and appetite. These sit right next to side effects in most conversations with a provider, so it helps to keep them in the same place.

Keeping it all in one place

The hardest part of tracking is not knowing what to write. It is having doses, symptoms and weight scattered across a notes app, a calendar and a paper card.

If you would rather keep everything together, Peppy is a peptide and GLP-1 tracker for iPhone that lets you log side-effect check-ins from mild to severe right next to your doses and weight. You can see how it handles this on the weight and side-effect tracking help page, and the dose history feature shows doses logged, missed and on time. Your data stays on your iPhone and your own iCloud backup, which you can read about in the privacy policy.

Whatever tool you use, the goal is the same: a clear, honest record that helps you and your provider make decisions together.

The short version

• Gastrointestinal effects like nausea and diarrhea are the most commonly reported GLP-1 side effects in major trials.
• Trials describe them as mostly mild to moderate, and tirzepatide's showed up mainly during dose escalation.
• Log the date, time, last dose, severity and duration every time, plus good days.
• Describe, do not diagnose, and bring the trend to your provider.
• Anything severe or serious goes to your provider or urgent care right away, not into a log to review later.