You've been on Wegovy for months. The weight's coming off, but not as fast as you'd hoped. You've read about Mounjaro's better results and you're ready to make the switch. But here's the question that's been nagging at you: do you really need to wait a whole week between medications, or can you just swap straight over?

It's a fair question. A week without medication means your appetite creeping back. It means watching that number on the scales potentially tick upward. It means undoing some of the hard work you've put in.

The short answer: you need a gap of at least 7 days. The longer answer explains why that gap actually protects you and sets you up for better results with Mounjaro.

Why You Can't Switch From Wegovy to Mounjaro Straight Away

Both medications work on your GLP-1 receptors, but they're not identical. Wegovy contains semaglutide, which targets GLP-1 alone. Mounjaro contains tirzepatide, which targets both GLP-1 and GIP receptors. This dual action is why Mounjaro often delivers stronger weight loss results.

Here's the problem: semaglutide has a half-life of approximately 7 days. That means a week after your last Wegovy injection, half the medication is still in your system After two weeks, roughly a quarter remains. It takes around 4-5 weeks for Wegovy to fully clear from your body.

If you add Mounjaro on top before the Wegovy has sufficiently cleared, you're essentially doubling up on GLP-1 stimulation. That's not twice as effective. It's a recipe for severe nausea, vomiting, and digestive problems that could put you off treatment entirely.

How Long Does Wegovy Stay in Your System?

Understanding Wegovy's pharmacokinetics helps explain why the washout period matters:

• Half-life: Approximately 7 days (168 hours)


• Time to clear: ~4–5 weeks for full elimination


• Steady state: Reached after ~4–5 weeks of consistent dosing


• Peak concentration: 1–3 days after injection

By comparison, Mounjaro (tirzepatide) has a shorter half-life (~5 days), meaning it clears in ~25–30 days.

What Actually Happens During the 7-Day Washout Period

Here's what most providers won't tell you: the gap isn't as dramatic as you might fear. Wegovy's long half-life means it doesn't vanish from your system the moment you stop injecting. The appetite-suppressing effects continue for several days.

• Days 1-3: You'll likely notice very little difference. Wegovy is still working in your system at roughly 70-85% strength, keeping your appetite in check.


• Days 4-5: Your appetite may start returning gradually. Some patients notice increased hunger or food thoughts creeping back. Medication is at roughly 50-60% strength.


• Days 6-7: Effects are diminishing but haven't disappeared. You're about to start Mounjaro. Any appetite increase is temporary.

Most patients report gaining little to no weight during this week, especially if they stick to the healthy eating habits they've developed during treatment. The fear of losing progress is usually worse than the reality.

Will I Gain Weight During the Washout Period?

This is the question that keeps patients up at night. The honest answer: most people don't gain significant weight during a 7-day gap.

Because semaglutide stays active in your body for days after your last injection, you don't experience a sudden return of appetite. Any weight fluctuation during this week is more likely water retention or normal daily variation than actual fat gain.

The patients who struggle during the washout period are typically those who abandon their healthy eating habits entirely, assuming the medication was doing all the work. If you continue eating mindfully and staying active, you'll get through the week without undoing your progress.

What If I Need a Longer Gap Between Medications?

Some clinicians recommend longer washout periods of 7-14 days, particularly if you've experienced severe side effects on Wegovy. A longer gap allows more of the semaglutide to clear, potentially reducing the intensity of side effects when you start tirzepatide.

If you're having surgery, your healthcare team may ask you to stop GLP-1 medications further in advance. The MHRA has issued guidance about the risk of residual gastric contents during anaesthesia because these medications slow stomach emptying.

What Dose of Mounjaro Will You Start On After Wegovy?

This is where having the right provider makes a real difference. Some clinics start everyone on the lowest 2.5mg dose regardless of their Wegovy history. That's the cautious approach, but it means you might spend weeks on doses that don't suppress your appetite as effectively as your previous Wegovy dose did.

Because you've already been on a GLP-1 medication, your body has developed some tolerance to the class. A clinician reviewing your treatment history may recommend starting at a higher Mounjaro dose than someone completely new to these medications.

Typical starting dose recommendations based on Wegovy dose:

• Wegovy 0.25mg-0.5mg: Usually start Mounjaro at 2.5mg


• Wegovy 1mg: May start Mounjaro at 2.5mg or 5mg


• Wegovy 1.7mg-2.4mg: May start Mounjaro at 5mg or higher

Important: These are general guidelines only. Your actual starting dose depends on your individual tolerance, side effect history, and clinical assessment. Never adjust doses without medical guidance.

How to Switch From Wegovy to Mounjaro Safely: Step-by-Step

Making the switch doesn't have to be complicated. Here's what a safe transition looks like:

Why Are Patients Switching From Wegovy to Mounjaro?

Wegovy works. It's helped thousands of people lose significant weight. But Mounjaro's dual-action approach often delivers better results for patients who've plateaued or want to maximise their weight loss.

Clinical trials tell a compelling story: Mounjaro users lost up to 22.5% of their body weight over 72 weeks on the highest dose (SURMOUNT-1 trial), compared to around 15-17% with Wegovy over 68 weeks (STEP-1 trial). For many patients, that difference of 5-7% represents several stone of additional weight loss.

Other reasons patients switch:

• Weight loss plateau: Results have stalled despite being on the maximum Wegovy dose


• Side effect tolerance: Some patients tolerate Mounjaro better than Wegovy (or vice versa)


• Blood sugar benefits: Mounjaro's dual action may offer better glucose control for those with prediabetes


• Personal preference: Some simply want to try the newer medication

Why Switch to Mounjaro With G-1 Nutrition?

Switching medications is one thing. Switching providers at the same time gives you the opportunity to upgrade your entire treatment experience.

Many patients switching from Wegovy to Mounjaro are also leaving providers who've disappointed them. Slow responses to urgent questions about side effects. Rigid dosing protocols that don't account for individual needs. Hidden fees that made treatment more expensive than advertised.

G-1 Nutrition offers:

• Transparent pricing with no surprise charges


• Responsive clinical support from GPhC-registered pharmacists


• Individualised dosing recommendations based on your treatment history


• Flexible consultation scheduling that works around your life


• No restrictive contracts