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GLP-1 side effects

You are dealing with a symptom and want to know if it is expected.

Reference and calculator, not medical advice. Dosing figures below are transcribed from FDA-approved prescribing information and link back to it. Last reviewed August 2026.

Almost everything reported with GLP-1 receptor agonists is gastrointestinal, and almost all of it clusters around dose increases rather than being constant. That pattern is the single most useful thing to understand: the stepped titration schedule exists precisely because escalation speed, not the drug itself, drives most of what people experience.

Listed in the prescribing information

Common adverse reactions listed for GLP-1 receptor agonists as a class.

These products carry a boxed warning regarding thyroid C-cell tumours observed in rodent studies, and are contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN 2. Read the full prescribing information for your specific product and discuss it with your prescriber — this summary is not complete and is not a substitute for that document.

Below is when things typically occur relative to the schedule. This is a structural map of the dosing timeline, not a prediction — individual experience varies widely, and plenty of people go through the whole escalation with very little.

Common questions

Why is it always worst right after a dose increase?
Each step raises the drug concentration your system is adapting to. The prescribing information builds in four-week holds between steps for exactly this reason. When people describe a bad week, it very often maps onto the days following an escalation.
Does it get better if I stay at the same dose?
Gastrointestinal effects are generally described as easing with continued exposure at a stable dose. This is why holding at a step, rather than pushing to the next one on schedule, is such a common adjustment prescribers make.
What is the boxed warning about?
These products carry a boxed warning regarding thyroid C-cell tumours observed in rodent studies. They are contraindicated in people with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2. This is a contraindication to screen for before starting, not a side effect that develops.
What is not on the label but comes up constantly?
Hair shedding and loss of muscle mass are two things people report frequently that are better understood as consequences of rapid weight loss in general than as direct drug effects. Both are discussed on their own pages here.
When should I stop reading and call someone?
Severe or persistent abdominal pain, persistent vomiting, signs of dehydration, or anything that feels unlike the pattern above. Online information cannot triage a symptom, and this is the category where waiting to see is the wrong call.

Side-by-side

Structural facts from each product’s prescribing information.

ProductActive ingredientIndicationFrequencyStartMax labelledSteps to max
Zepbound
Eli Lilly		TirzepatideWeight managementWeekly2.5 mg15 mg6
Mounjaro
Eli Lilly		TirzepatideType 2 diabetesWeekly2.5 mg15 mg6
Wegovy
Novo Nordisk		SemaglutideWeight managementWeekly0.25 mg2.4 mg5
Ozempic
Novo Nordisk		SemaglutideType 2 diabetesWeekly0.25 mg2 mg4
Saxenda
Novo Nordisk		LiraglutideWeight managementDaily0.6 mg3 mg5
Trulicity
Eli Lilly		DulaglutideType 2 diabetesWeekly0.75 mg4.5 mg4

One structural difference worth noting across products: the number of escalation steps varies. Tirzepatide runs six steps to its maximum, semaglutide for weight management runs five, and liraglutide escalates weekly rather than monthly. More steps means smaller jumps, which is a different experience of the same process.

mg → syringe units converter

U-100 syringe. Formula: (dose ÷ concentration) × 100.

12.5units on a U-100 syringe
= 0.125 mL  ·  2.5 mg at 20 mg/mL

Check the concentration printed on the vial you are actually holding. The same dose in milligrams is a completely different mark on the syringe at a different concentration. If the number here does not match what your prescriber told you, trust your prescriber.

Sources and last review

Every dosing figure on this page is transcribed from an FDA-approved label and links back to it. Conversions are arithmetic you can repeat by hand. Nothing here is reviewed by a clinician, and this site does not employ one — which is exactly why what I do publish stays traceable to its source.

Transcribed from the labels above and checked by me — Gavin, who builds this site, takes a GLP-1, and is not a clinician. Last reviewed August 2026. Found an error? [email protected] — I treat corrections as bugs. How this site is built and funded.

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