Which GLP-1 has the fewest side effects?

The labels do not answer that, and a page that ranks them is inventing the ranking. Each label reports its own trial under its own protocol, and the products were never compared head to head, so a shorter list can mean a smaller trial rather than a gentler drug. What is comparable is which reaction appears on which label, which is the table above.

Which of these carry a boxed warning?

Contrave, Foundayo, Mounjaro, Ozempic, Rybelsus, Saxenda, Trulicity, Victoza, Wegovy pill, Wegovy and Zepbound. A boxed warning is the FDA's most serious label warning and it is not the same as a common side effect — it is a specific risk with a specific contraindication attached, set out on each drug's own page here.

How long do the side effects last?

For the gut reactions, they cluster in the days after each dose increase and settle in between, so the pattern is a few rough days per step rather than one continuous stretch — which means the honest answer depends on that drug's titration schedule. A drug reaching its maintenance dose at week 5 stops stepping up long before one that takes 17. Each symptom page here sets the reaction against its own drug's published schedule.

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GLP-1 side effects, from the labels

Bottom line

No reaction is on all 13 labels read here. Nausea, diarrhea and vomiting are on all 10 GLP-1 labels. That makes them a property of the class rather than of any brand, so switching between GLP-1s is not a way out. 18 reactions appear on some labels and not others, which is the part worth checking before you choose. Everything below is quoted from each product's own FDA prescribing information, with the date that label was published.

Last updated 2026-09-02 — the newest FDA label read here. Read and dated by Alex Seot.

What are the side effects of GLP-1 medications?

The 10 GLP-1 labels among the 13 weight-loss products tracked here all list nausea, diarrhea and vomiting. One mechanism explains most of it: GLP-1 drugs slow how fast the stomach empties. That is how they produce the fullness that makes them work and also how they produce nausea, so the two arrive together rather than one being a malfunction. Contrave, Phentermine and Qsymia are not GLP-1s and work differently; the reactions all of their labels list include constipation, dizziness, insomnia and dry mouth. Listed on a label means it was seen often enough in a trial to be printed, not that it happens to everyone. Contrave, Foundayo, Mounjaro, Ozempic, Rybelsus, Saxenda, Trulicity, Victoza, Wegovy pill, Wegovy and Zepbound additionally carry a boxed warning, which is a different thing from a common reaction: a specific risk with a specific contraindication attached. The labels cannot say which drug is gentlest, and any page that ranks them is inventing the ranking. Each reports its own trial under its own protocol and none was compared head to head, so a shorter list can mean a smaller trial. What is comparable is which reaction appears on which label, and the timing. The gut reactions cluster in the days after each dose increase, so how long they last depends on that drug's own titration schedule rather than on the class.

Which reaction is on which label

A tick means the reaction is named among the common adverse reactions on that product's own FDA label. An empty cell means it is not on that label — not that it never happens. Contrave, Phentermine and Qsymia are not GLP-1s; they are in the table for comparison.

Reaction	Contrave	Foundayo	Mounjaro	Ozempic	Phentermine	Qsymia	Rybelsus	Saxenda	Trulicity	Victoza	Wegovy pill	Wegovy	Zepbound
nausea	✓	✓	✓	✓	—	—	✓	✓	✓	✓	✓	✓	✓
fatigue	—	✓	—	—	—	—	—	✓	—	—	✓	✓	✓
constipation	✓	✓	✓	✓	✓	✓	✓	✓	—	✓	✓	✓	✓
diarrhea	✓	✓	✓	✓	✓	—	✓	✓	✓	✓	✓	✓	✓
vomiting	✓	✓	✓	✓	—	—	✓	✓	✓	✓	✓	✓	✓
hair loss	—	✓	—	—	—	—	—	—	—	—	—	✓	✓
injection site reactions	—	—	—	—	—	—	—	✓	—	—	—	—	✓
abdominal pain	—	✓	✓	✓	—	—	✓	✓	✓	—	✓	✓	✓
indigestion	—	✓	✓	—	—	—	—	✓	—	✓	✓	✓	✓
reflux	—	✓	—	—	—	—	—	—	—	—	—	✓	✓
burping	—	✓	—	—	—	—	—	—	—	—	—	✓	✓
bloating	—	✓	—	—	—	—	—	—	—	—	✓	✓	—
dizziness	✓	—	—	—	✓	✓	—	✓	—	—	✓	✓	—
headache	✓	✓	—	—	✓	—	—	✓	—	—	✓	✓	—
insomnia	✓	—	—	—	✓	✓	—	—	—	—	—	—	—
dry mouth	✓	—	—	—	✓	✓	—	—	—	—	—	—	—
decreased appetite	—	—	✓	—	—	—	✓	—	✓	✓	—	—	—
low blood sugar	—	—	—	—	—	—	—	✓	—	—	—	✓	—

The boxed warnings

The FDA's most serious label warning. Not a common side effect — a specific risk with a contraindication attached.

Contrave
Bupropion raises the risk of suicidal thoughts and behavior in children, adolescents and young adults. The label carries that as a boxed warning and tells prescribers to watch for mood changes, particularly in the first months and after any dose change.
Foundayo
The label carries the GLP-1 class boxed warning for thyroid C-cell tumors, and says why it applies here: GLP-1 receptor agonists that are pharmacologically active in rats and mice caused thyroid C-cell tumors at clinically relevant exposures. Orforglipron is not pharmacologically active in rats or mice and did not produce tumors in rodents; because it is active at the human GLP-1 receptor, the label says the human relevance of those rodent tumors has not been determined. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Mounjaro
In rodents this molecule caused thyroid C-cell tumors at human-relevant doses. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Ozempic
In rodents this molecule caused thyroid C-cell tumors at human-relevant doses. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Rybelsus
In rodents this molecule caused thyroid C-cell tumors. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Saxenda
In rodents this molecule caused thyroid C-cell tumors at human-relevant doses. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Trulicity
In rats this molecule caused thyroid C-cell tumors. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Victoza
In both sexes of rats and mice this molecule caused thyroid C-cell tumors at clinically relevant exposures. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Wegovy pill
In rodents this molecule caused thyroid C-cell tumors at clinically relevant exposures. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Wegovy
In rodents this molecule caused thyroid C-cell tumors at human-relevant doses. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.
Zepbound
In rodents this molecule caused thyroid C-cell tumors at human-relevant doses. Whether it does so in people is unknown, and the label carries that as a boxed warning. It is contraindicated outright with a personal or family history of medullary thyroid carcinoma or MEN 2.

Every label, and every reaction on its own page

Contrave side effects FDA label, published 2025-11-17

nausea, constipation, headache, vomiting, dizziness, insomnia

nausea →constipation →diarrhea →vomiting →dizziness →headache →insomnia →dry mouth →

Foundayo side effects FDA label, published 2026-08-13

nausea, constipation, diarrhea, vomiting, indigestion, abdominal pain

nausea →fatigue →constipation →diarrhea →vomiting →hair loss →abdominal pain →indigestion →reflux →burping →bloating →headache →

Mounjaro side effects FDA label, published 2026-09-02

nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion

nausea →constipation →diarrhea →vomiting →abdominal pain →indigestion →decreased appetite →

Ozempic side effects FDA label, published 2026-06-10

nausea, vomiting, diarrhea, abdominal pain, constipation

nausea →constipation →diarrhea →vomiting →abdominal pain →

Phentermine side effects FDA label, published 2026-06-15

raised heart rate, raised blood pressure, restlessness, dizziness, insomnia, headache

constipation →diarrhea →dizziness →headache →insomnia →dry mouth →

Qsymia side effects FDA label, published 2026-04-24

tingling in the hands and feet, dizziness, altered taste, insomnia, constipation, dry mouth

constipation →dizziness →insomnia →dry mouth →

Rybelsus side effects FDA label, published 2026-08-19

nausea, abdominal pain, diarrhea, decreased appetite, vomiting, constipation

nausea →constipation →diarrhea →vomiting →abdominal pain →decreased appetite →

Saxenda side effects FDA label, published 2026-06-15

nausea, low blood sugar in people with type 2 diabetes, diarrhea, constipation, vomiting, headache

nausea →fatigue →constipation →diarrhea →vomiting →injection site reactions →abdominal pain →indigestion →dizziness →headache →low blood sugar →

Trulicity side effects FDA label, published 2026-08-10

nausea, diarrhea, vomiting, abdominal pain, decreased appetite

nausea →diarrhea →vomiting →abdominal pain →decreased appetite →

Victoza side effects FDA label, published 2025-11-17

nausea, diarrhea, vomiting, decreased appetite, indigestion, constipation

nausea →constipation →diarrhea →vomiting →indigestion →decreased appetite →

Wegovy pill side effects FDA label, published 2026-06-30

nausea, diarrhea, vomiting, constipation, abdominal pain, headache

nausea →fatigue →constipation →diarrhea →vomiting →abdominal pain →indigestion →bloating →dizziness →headache →

Wegovy side effects FDA label, published 2026-06-30

nausea, diarrhea, vomiting, constipation, abdominal pain, dysesthesia — altered skin sensation such as tingling or burning, mostly at 7.2 mg

nausea →fatigue →constipation →diarrhea →vomiting →hair loss →abdominal pain →indigestion →reflux →burping →bloating →dizziness →headache →low blood sugar →

Zepbound side effects FDA label, published 2026-09-02

nausea, diarrhea, vomiting, constipation, abdominal pain, indigestion

nausea →fatigue →constipation →diarrhea →vomiting →hair loss →injection site reactions →abdominal pain →indigestion →reflux →burping →

Which is best, by what you want →Ozempic face, and what going slower costs →Hair loss: which labels list it →Alcohol: what the labels say →GLP-1s and pregnancy →GLP-1s and birth control →GLP-1s and PCOS →GLP-1s and cancer →GLP-1s before surgery →GLP-1s and sleep apnea →GLP-1s and depression →GLP-1s and inflammation →GLP-1s and menopause →GLP-1s and dementia →Every verified price, ranked →What a first year costs →Everything on semaglutide →Everything on tirzepatide →

No clinician has reviewed this page. Label and trial statements are quoted from the FDA label or the trial cited beside them. General guidance is marked as such, and every price carries the date it was verified. That is sourcing, not medical review. What we do and do not check · Who checked the price

GLP-1 side effects, answered

Which GLP-1 has the fewest side effects?: The labels do not answer that, and a page that ranks them is inventing the ranking. Each label reports its own trial under its own protocol, and the products were never compared head to head, so a shorter list can mean a smaller trial rather than a gentler drug. What is comparable is which reaction appears on which label, which is the table above.
Which of these carry a boxed warning?: Contrave, Foundayo, Mounjaro, Ozempic, Rybelsus, Saxenda, Trulicity, Victoza, Wegovy pill, Wegovy and Zepbound. A boxed warning is the FDA's most serious label warning and it is not the same as a common side effect — it is a specific risk with a specific contraindication attached, set out on each drug's own page here.
How long do the side effects last?: For the gut reactions, they cluster in the days after each dose increase and settle in between, so the pattern is a few rough days per step rather than one continuous stretch — which means the honest answer depends on that drug's titration schedule. A drug reaching its maintenance dose at week 5 stops stepping up long before one that takes 17. Each symptom page here sets the reaction against its own drug's published schedule.

Every cell is read from that product's own FDA prescribing information, linked on its page with the date the label was published. Information only, not medical advice — a symptom that worries you is a call to your prescriber, not a search result.