GLP-1 side effects: what to track and when to call your clinician

Most people starting Mounjaro, Wegovy, Ozempic or Saxenda get some side effects. Most of them are gastrointestinal — nausea, mild reflux, slower-than-usual digestion, fatigue, headache, occasional diarrhoea or constipation. Most of them fade as the body adjusts to the dose, particularly after a dose increase. A small number don’t fade, or signal something that needs attention. This guide is about telling those apart.

Tracking matters here because GLP-1 side effects are patterned. They tend to peak 24 to 48 hours after a shot, taper into the back half of the week, and flare again after a dose increase. Without a log, every wave feels like the first wave. With a log, you start to see — oh, this is the usual Thursday dip, not a new problem.

The common side effects worth logging

The list below covers what shows up most often in GLP-1 clinical trials and in real-world reporting. None of this replaces talking to your prescriber — but knowing the categories helps you keep a useful record.

Gastrointestinal

• Nausea.The most common. Often peaks Day 1–2 post-injection. Note the severity (mild, moderate, severe) and how long it lasts.
• Reflux / heartburn. Can flare after fatty or large meals. Log timing relative to meals.
• Vomiting. Always worth noting, especially if it happens more than once per shot cycle.
• Constipation. The single most under-tracked GLP-1 side effect. Note how many days since the last bowel movement and whether you needed laxatives.
• Diarrhoea. Less common than constipation but happens, particularly in the first weeks.
• Stomach pain or cramping. Mild is normal; sharp, severe, or escalating is not (see red flags below).

Energy and mood

• Fatigue. Particularly in the first 48 hours after a dose. Often improves with adequate water and protein.
• Headache. Frequently dehydration-driven on GLP-1s. Worth logging alongside water intake.
• Mood changes. Less talked about but real for some people. Note any persistent change in mood, anxiety or sleep.

Injection-site reactions

• Mild redness or itching at the site for a few hours is common.
• Bruising can happen even with correct technique.
• Persistent warmth, swelling, or a hard lump a day or more after injection is worth flagging.

What to record (so the log is actually useful)

For each entry, four fields are enough:

1. What.The symptom in one or two words: “nausea”, “reflux”, “fatigue”.
2. How bad.A 1–3 or 1–5 severity scale. Stop overthinking the number — consistency matters more than accuracy.
3. When. Date and time. The whole point is to see the time-since-shot pattern.
4. Context.One sentence: “after coffee on an empty stomach”, “3 hours after lunch”. Don’t write essays. The pattern emerges across many small notes.

The patterns to look for over a month

• Day-of-week clustering.If nausea piles up on Tuesday and your shot is Monday morning, that’s your standard curve. Plan softer meals and lighter days around it.
• Post-titration flares. Side effects often spike for one to two weeks after a dose increase, then settle. Knowing this stops you from blaming the new dose permanently.
• Trigger foods. Some users find that fatty foods, fried foods, alcohol, or large portions reliably trigger nausea or reflux on a GLP-1. The log spots the pattern faster than memory.
• Trend, not single events. One rough day is not a trend. Three rough Tuesdays in a row is.

When to call your prescriber

Common GLP-1 side effects are uncomfortable, not dangerous. A few symptoms cross that line. Call your clinician promptly — not next week — if you have any of the following:

• Severe, persistent abdominal pain, particularly if it radiates to your back, doesn’t ease with positioning, or comes with vomiting. This can be a sign of pancreatitis, a rare but serious GLP-1 risk.
• Persistent vomitingthat you can’t keep fluids down for > 24 hours.
• Signs of dehydration: dark urine, dizziness on standing, very dry mouth, confusion.
• Severe constipation with bloating, no bowel movement for 4+ days, and abdominal pain.
• Right-upper-abdomen pain, yellowing of the skin or eyes, dark urine and pale stools: possible gallbladder issue (GLP-1s can increase gallstone risk during rapid weight loss).
• Vision changes if you have diabetes (rapid blood sugar drops can affect the retina).
• Allergic reaction: swelling of lips, tongue or throat, hives, difficulty breathing. This is a 999 / 911 call, not a clinician call.
• Persistent low mood or thoughts of self-harm. GLP-1s are not the cause for most people but mood changes can occur and should always be discussed.

Things that help (and are not medical advice)

Most clinicians offering GLP-1 prescriptions repeat the same practical suggestions for managing mild side effects. They’re worth logging so you can see what actually works for you:

• Smaller portions, eaten more slowly. GLP-1s slow stomach emptying; a full plate often becomes uncomfortable.
• Front-load protein and fluids early in the day. By evening, the fullness signal can dominate.
• More water than feels necessary — dehydration drives a lot of GLP-1 headaches and fatigue.
• Lighter, cooler food on Day 1–2 post-shot if you’re someone whose nausea pattern is clear.
• Move a little. Even a short walk after meals helps with reflux and stomach comfort for many people.

How Akoma handles this

Akomaincludes a quiet side-effect log alongside the injection tracker, so each shot and the symptoms that follow live next to each other. Over a few weeks you can see your post-shot curve clearly — without needing to think about it between shots. Logs stay on your device; we don’t sell side-effect data and we don’t train models on it.

Akoma is free to download on the Apple App Store and is available worldwide.

Related reading

• Mounjaro injection sites: a complete rotation guide
• Best GLP-1 tracker apps in 2026: an honest comparison