GLP-1 Side Effects — What's Common, What's Serious, What to Track

It's the second evening after your first dose step. Dinner looked good an hour ago; now half a plate feels like a mistake, and there's a low, seasick hum that wasn't there last week. Is this normal? Is it the dose? Will it pass?

For most people on a GLP-1, the honest answer is: probably, very likely, and usually. Here's how to tell the difference between "adjusting" and "call someone".

Which side effects are most common?

Across the prescribing information for semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound), the most frequently reported side effects are gastrointestinal:

• Nausea, especially early on and after dose increases
• Diarrhea and vomiting
• Constipation
• Abdominal pain, indigestion and bloating
• Decreased appetite — expected, but worth watching so you still eat enough
• Fatigue

These medications slow how quickly your stomach empties and quiet appetite signals. That's how they work, and it's also why your gut notices first.

Why do they cluster around dose changes?

Doses go up gradually — usually every four weeks — so your body can adjust. Side effects tend to peak in the first days after starting or stepping up, then ease. That rhythm is the most useful thing you can learn about your own body, because it tells you whether a symptom is familiar adjustment or something new.

What helps with the everyday ones?

General approaches from clinical nutrition guidance — check with your own care team:

• Eat smaller amounts and stop at the first sign of fullness; it arrives sooner now.
• Go gently with very fatty, fried or rich food, which often makes nausea worse.
• Keep sipping fluids, especially with vomiting or diarrhea.
• Put protein and fiber first in the smaller portions you do eat, adding fiber gradually if you're constipated.

Which side effects need a doctor?

These are less common, but the labels list them and they need prompt attention:

• Pancreatitis — severe, persistent abdominal pain that may spread to your back, with or without vomiting
• Gallbladder problems — pain in the upper right abdomen, fever, yellowing of the skin or eyes
• Kidney problems — dehydration from vomiting or diarrhea can affect kidney function
• Low blood sugar — mainly when combined with insulin or a sulfonylurea
• Serious allergic reactions — swelling of the face, lips or throat; trouble breathing
• Thyroid C-cell tumors — the labels carry a boxed warning; report a lump in your neck, trouble swallowing or a hoarse voice

What we'd track

A short record you keep beats a perfect one you abandon. For each symptom:

1. What it was, and how strong — mild, moderate or severe is enough.
2. When it started relative to your last dose — hours or days.
3. How long it lasted.
4. What you'd eaten and drunk that day.
5. What helped, if anything did.

Holt lines every entry up against your dose days and dose steps, so "it got worse after I went up" is something you can see, not something you have to remember.

Log side effects against your doses in Holt