The best weight loss injection

The three approved injections

By average weight loss in trials, Zepbound is the strongest approved injection, followed by Wegovy and then Saxenda.

Separate trials, so compare with care. The head-to-head SURMOUNT-5 trial found about 20.2% average loss on tirzepatide vs about 13.7% on semaglutide. Full side-by-side: Zepbound vs Wegovy.

Side effects compared

Stomach side effects are the most common on all three. Here's how often they showed up in each label's weight-management trials, with the placebo rate in brackets:

These come from separate trials, so they aren't a direct comparison. Most effects were mild to moderate and showed up most while the dose was going up. See what to expect week by week with the side-effect timeline.

How the doses step up

All three labels start low and climb slowly. These are the label schedules, as of our last review. Your prescriber sets your own pace and may slow it down if side effects are rough.

The Saxenda label also says to stop if you haven't lost at least 4% of your body weight after 16 weeks on treatment.

What using one at home looks like

• The pen goes into the skin of your stomach, thigh or upper arm. The needle is small, and most people say it's easier than they expected.
• You rotate the spot each time.
• Pens live in the fridge. Each label allows some time out of it: up to 21 days at or below 86°F for Zepbound, up to 28 days for Wegovy, and up to 30 days after first use for Saxenda. Details: Zepbound storage, Wegovy storage and Saxenda storage.
• Weekly shots go on the same day each week, at any time of day, with or without food.
• Doses start low and step up over weeks so your stomach can adjust. Map yours with the dose schedule.
• Flying soon? Read traveling with GLP-1 pens.

Which one might fit you

• You want the largest average loss: Zepbound has the biggest trial numbers so far.
• You have heart disease: Wegovy is the injection approved to lower the risk of heart attack and stroke in adults with heart disease and obesity or overweight.
• You have sleep apnea: Zepbound is approved for moderate to severe obstructive sleep apnea in adults with obesity.
• You're a teen, or a parent of one: Wegovy and Saxenda have approvals for some children 12 and older.
• You'd rather skip needles: ask about the Wegovy pill instead.

These are starting points for a conversation. A licensed clinician weighs them against your full health history.

What about Ozempic and Mounjaro

They're injections with the same medicines, but they're approved for type 2 diabetes, not weight management. Prescribers usually use the weight-approved brands when weight is the goal. More: is Ozempic a weight-loss drug?

Injections to avoid

The FDA has warned about unapproved and counterfeit GLP-1 products sold online, sometimes without a prescription. Compounded versions aren't FDA-approved, and dosing errors have sent people to the hospital. Read where compounded GLP-1s stand.

Warning signs include a seller that skips the prescription, vials labeled "for research only", doses measured in syringe "units", and pens whose packaging doesn't match the brand. A licensed pharmacy filling a real prescription is the safest route.

When to talk to your doctor

• Before starting any injection, and before any dose increase.
• If you have a personal or family history of medullary thyroid cancer or MEN 2.
• If you get severe stomach pain, signs of dehydration, or a lump in your neck.
• If you have surgery or a procedure with anesthesia coming up.