Wegovy side effects: what is common and what is serious

Wegovy pen 2.4 mg: the reactions people report most

Section 6.1 of the Wegovy label lists each reaction next to its placebo rate from the adult weight studies. The 2.4 mg pen is the usual long-term dose, so it is the fairest place to start ^[1].

Share of adults reporting each reaction, 2.4 mg pen vs placebo

Reaction	Wegovy vs placebo
Feeling sick (nausea)	44% vs 16%
Loose stools (diarrhea)	30% vs 16%
Throwing up	24% vs 6%
Constipation	24% vs 11%
Belly pain	20% vs 10%
Headache	14% vs 10%
Tiredness	11% vs 5%
Indigestion	9% vs 3%
Dizziness	8% vs 4%

Placebo groups had many of the same complaints, which is why the gap matters more than the headline number. Burping, gas, a swollen-feeling belly, reflux and stomach bugs were also logged more often on Wegovy ^[1]. The rarer, serious warnings get their own section lower down.

Higher dose and pill: how the numbers shift

The 7.2 mg pen. Two 72-week studies compared 7.2 mg, 2.4 mg and placebo. Nausea came in at 39%, 35% and 13%; throwing up at 22%, 16% and 6%; constipation at 20%, 19% and 8%; hair loss at 6%, 3% and 1% ^[1]. A tingling or altered skin sensation called dysesthesia was the standout: 22% on 7.2 mg against 6% on 2.4 mg ^[1]. In each active group, 5% quit over side effects; on placebo, 2% did ^[1].

The 25 mg tablet. Per the label, reactions on the pill matched the 2.4 mg pen in kind and in how often they happened. Dysesthesia showed up in 5%, compared with 0% on placebo, and 6.9% stopped for side effects compared with 5.9% ^[1]. The two forms are set side by side in Wegovy pill vs injection.

Energy, headaches and sleep on Wegovy

Low energy is a listed reaction (11% vs 5%), and so is headache (14% vs 10%) ^[1]. Feeling lightheaded ran 8% vs 4% ^[1]. The label makes no promise of extra energy. Tiredness paired with nonstop vomiting or diarrhea is a reason to phone your prescriber, since running low on fluids can hurt the kidneys (Section 5.5) ^[1].

Trouble sleeping, anxiety, a dry mouth, lower sex drive, needing to pee more, aches and period changes did not appear in the Section 6.1 reaction lists we read, so we have no rates to give. That is not proof they never happen. Mention them at your next visit.

Why the gut reacts, and for how long

Wegovy delays how quickly food leaves the stomach ^[1]. On the pen, the 16-week ramp to the maintenance dose is when nausea, diarrhea and similar complaints were logged most ^[1]. STEP 1, the main 2.4 mg trial, described its nausea and diarrhea as usually short-lived and mild or moderate ^[2]. No source we used gives a day count.

Post-approval reports describe ileus (a bowel that stops moving), intestinal blockage and constipation bad enough to cause fecal impaction ^[1]. The label does not say whether these clear up. Belly pain, bloating or vomiting that is severe or will not ease needs a prompt call.

Rare but serious: the label warnings

• Inflamed pancreas: 0.2 cases per 100 patient-years on Wegovy, under 0.1 on placebo; post-approval reports include necrotizing cases and deaths ^[1].
• Gallstones: pen 1.6% vs 0.7%; tablet 2.5% vs 1% ^[1].
• Kidney damage when vomiting or diarrhea drains your fluids ^[1].
• Hypoglycemia for people with type 2 diabetes, more so alongside insulin or a sulfonylurea ^[1].
• Pulse: resting heart rate ran 1 to 4 beats per minute above placebo on average ^[1].
• Eyes: diabetic retinopathy complications in people with type 2 diabetes ^[1].
• Anesthesia: stomach contents can be inhaled during deep sedation or general anesthesia ^[1].
• Allergy: anaphylaxis and angioedema have been reported ^[1].

One more rule from the label: a FlexTouch pen is for one person only, even if the needle is swapped ^[1].

Hair, muscle, thyroid and mood

Hair. Thinning was logged in 3.3% on 2.4 mg, 5.8% on 7.2 mg and 1% on placebo ^[1]. Muscle. We found no muscle loss rate in the label sections we read; our page on keeping muscle on a GLP-1 covers protein and strength work.

Thyroid. Wegovy's boxed warning rests on rodent studies, where semaglutide caused thyroid C-cell tumors. Whether it does the same in people, including medullary thyroid carcinoma, has not been shown either way ^[1]. Anyone with MEN 2, or with MTC in themselves or a close relative, should not take it ^[1]. We cannot say whether any one person's thyroid cancer was caused by Wegovy.

Mood. In February 2026 the warning on suicidal behavior and ideation came off both the Wegovy and Zepbound labels ^[3]. Any change in mood is still worth raising with your prescriber.

Practical ways to ease Wegovy side effects

• Slow the climb. When a step-up is rough, the label lets your prescriber hold off the next increase for 4 weeks ^[1].
• On the pill? Swallow it with an empty stomach and at most 4 ounces of plain water, then hold off food, other drinks and pills for 30 minutes ^[1]. This rule does not apply to the pen.
• Never take two shots to catch up. The 48-hour missed-dose rule is explained in how to use Wegovy.
• Keep pens in the temperature range the label sets; see Wegovy storage and, for compounded vials, semaglutide storage.

Sleep apnea? It is not one of Wegovy's approved uses, which are heart risk reduction, weight reduction and maintenance, and MASH ^[1]. Whether a cold pen stings more, or how to inject, is in the Instructions for Use in your carton. For the molecule-wide picture, read semaglutide side effects; for budgeting, see Wegovy cost.