Mounjaro vs Ozempic: Key Differences Explained

The Two Biggest Names in Weight Loss

If you've been researching weight loss injections, you've almost certainly come across Mounjaro and Ozempic (or its weight-loss-specific version, Wegovy). Both are weekly injections, both are prescription-only, and both have shown impressive results. But they're not the same.

Here's an honest, evidence-based comparison.

How They Work

Ozempic / Wegovy (Semaglutide)

• Targets GLP-1 receptors only
• Reduces appetite and slows gastric emptying
• Originally developed for type 2 diabetes (Ozempic), then approved for weight loss (Wegovy)

Mounjaro (Tirzepatide)

• Targets both GLP-1 and GIP receptors (dual-agonist)
• Same appetite-reducing effects as semaglutide PLUS additional metabolic benefits from GIP activation
• Approved for both type 2 diabetes and weight management

The dual mechanism is significant. GIP plays a role in fat metabolism and insulin sensitivity that GLP-1 alone doesn't fully address.

Weight Loss Results: Head to Head

The SURMOUNT and STEP clinical trial programmes provide direct comparison data:

*Sources: SURMOUNT-1 (2022), STEP 1 (2021)*

While individual results vary, the data consistently shows Mounjaro producing greater average weight loss.

Side Effects Comparison

Both medications share similar gastrointestinal side effects because they both activate GLP-1 receptors:

In clinical trials, discontinuation rates due to side effects were similar for both medications (approximately 4-7%).

Dosing

• Mounjaro: Starts at 2.5mg weekly, can be increased to 5mg, 7.5mg, 10mg, or 15mg
• Ozempic: Starts at 0.25mg weekly, increases to 0.5mg, then 1mg (up to 2mg)
• Wegovy: Starts at 0.25mg weekly, escalates monthly up to 2.4mg

Both use a gradual dose escalation to minimise side effects.

Availability in the UK

Both medications are available privately in the UK. NHS access is more limited:

• Ozempic is available on NHS for type 2 diabetes (not weight loss)
• Wegovy has limited NHS availability through specialist weight management services
• Mounjaro is increasingly available through private pharmacies like Roots Pharmacy

Which Should You Choose?

This is a decision for you and your prescriber. However, general considerations:

Mounjaro may be preferred if:

• You want the maximum possible weight loss
• You've tried semaglutide without sufficient results
• Your prescriber recommends the dual-agonist approach

Ozempic/Wegovy may be preferred if:

• You also have type 2 diabetes (longer track record for this)
• Mounjaro isn't available or affordable
• Your prescriber recommends starting with a single-agonist

The Bottom Line

Both Mounjaro and Ozempic are effective, evidence-based weight loss treatments. The clinical data gives Mounjaro an edge in average weight loss, which is why it has generated so much interest.

At Roots Pharmacy, we offer Mounjaro through our clinician-led consultation process. Every patient is assessed individually — because the best medication is the one that's right for you.