The Weight Loss Injections Explained: Semaglutide, Tirzepatide, and What's Coming Next

You've probably heard of Ozempic. Maybe Wegovy or Mounjaro. But now there's a whole new wave of metabolic drugs entering the scene, and the names are getting harder to pronounce.

This guide breaks down five of the biggest peptide drugs in development or already on the market, in plain English. No medical degree required.

First: What Are These Drugs, Anyway?

Your body naturally makes hormones that help control blood sugar and appetite. Three of the big ones are:

• GLP-1 tells your brain you're full, slows digestion, and lowers blood sugar.

• GIP works alongside GLP-1 to boost insulin after eating.

• Glucagon normally raises blood sugar, but when targeted carefully, it also revs up metabolism and fat burning.

The drugs below mimic one, two, or all three of these hormones at once. The more receptors a drug hits, generally the stronger the effect — but also the more complex the science.

The Five Drugs Compared

1. Semaglutide

Brand names: Ozempic / Wegovy | Targets: GLP-1 only | Status: FDA Approved

The one that started it all. Semaglutide mimics GLP-1, the "I'm full" hormone, so people eat less naturally and lose weight. It's taken as a weekly injection or daily pill.

Weight loss: Around 15% of body weight. Side effects: Nausea and constipation, especially early on.

2. Tirzepatide

Brand names: Mounjaro / Zepbound | Targets: GLP-1 + GIP | Status: FDA Approved

Tirzepatide is semaglutide's more powerful sibling. By adding GIP, it gets a stronger insulin response and seems to supercharge appetite suppression. In clinical trials, it clearly outperformed semaglutide on weight loss.

Weight loss: Around 20 to 22% of body weight. Side effects: Similar to semaglutide and generally well tolerated.

Analogy: If semaglutide is a one-two punch, tirzepatide is a one-two-three.

3. Retatrutide

Developer: Eli Lilly | Targets: GLP-1 + GIP + Glucagon | Status: In Clinical Trials

The first triple agonist in this class. Adding glucagon to the mix appears to rev up the metabolism and push the body to burn more fat, even at rest. Early trial results showed the most impressive weight loss numbers yet.

Weight loss: Up to around 24% of body weight. Side effects: Still being studied. Glucagon can slightly raise blood sugar, requiring careful balancing.

Analogy: Semaglutide is one instrument. Tirzepatide is a duet. Retatrutide is a full band.

4. Mazdutide

Developer: Innovent Biologics | Targets: GLP-1 + Glucagon | Status: In Trials (primarily China)

Mazdutide skips GIP and pairs GLP-1 with glucagon instead, aiming to combine appetite suppression with a metabolic boost. It's being developed mainly in China, and global data is more limited.

Weight loss: Around 10 to 15% in trials so far. Side effects: Being studied; less data than the others.

Think of it as: The metabolism-focused alternative to tirzepatide.

5. Survodutide

Developer: Boehringer Ingelheim + Zealand Pharma | Targets: GLP-1 + Glucagon |

Status: In Trials

Same hormone combo as mazdutide, but survodutide is turning heads for a different reason. Early evidence suggests it may be powerful for treating fatty liver disease (MASH/NAFLD), a condition with very few effective treatments today.

Weight loss: Around 18 to 19% in trials. Side effects: Still being studied.

Why it stands out: Most of these drugs compete purely on weight loss. Survodutide may win on liver health.

Side-by-Side Summary

Drug	Targets	Status	Est. Weight Loss
Semaglutide	GLP-1	Approved	~15%
Tirzepatide	GLP-1 + GIP	Approved	~20 to 22%
Retatrutide	GLP-1 + GIP + Glucagon	In Trials	~24%
Mazdutide	GLP-1 + Glucagon	In Trials	~10 to 15%
Survodutide	GLP-1 + Glucagon	In Trials	~18 to 19%

Which One Is "Best"?

Right now, tirzepatide is the gold standard for weight loss among approved drugs. Retatrutide could eventually surpass it if the trial results hold up at scale. Survodutide is most interesting for anyone dealing with fatty liver disease alongside obesity. And mazdutide is one to watch as more global data emerges.

The honest answer? The best drug is whichever one works safest for you, and that's a conversation worth having with your doctor.

The Bottom Line

We're in a genuinely historic moment in metabolic medicine. A drug class that barely existed 10 years ago is reshaping how doctors treat obesity, diabetes, and liver disease. All five of these drugs work with your body's own hormonal signals. The differences come down to which signals they target and how hard they push on each one.

This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before starting any medication.