Washout Periods Explained: Switching Safely Between Weight Loss Injections

If you’re moving from one weight loss injection to another, you may have heard the term “washout period.” It sounds a bit technical, but don’t worry — it simply refers to the short break you need to take between stopping one medicine and starting another.

Getting this timing right is really important for safety and effectiveness. Let’s take a closer look.

What Is a Washout Period?

A washout period is the gap between your last dose of one treatment and your first dose of another.

For weight loss injections like Mounjaro (tirzepatide), Wegovy (semaglutide), or Saxenda (liraglutide), this break is usually one full dosing interval.

That means:

• If you’ve been injecting weekly, your washout is one week.

• If you’ve been injecting daily (like Saxenda), your washout is one day.

Why Do You Need a Washout Period?

It might be tempting to jump straight from one pen to another, but that can cause problems. A washout period allows:

• Your body to stabilise – so drug levels don’t overlap.

• A safer switch – reduces risk of side effects like nausea, vomiting, or stomach pain.

• Better results – ensures your prescriber starts you at the correct new dose.

A Common Example: Mounjaro ➝ Wegovy

This is one of the most common switches we see at Ready Health. Here’s how it works:

• If you take your last Mounjaro injection on Friday 1st,

• Your first Wegovy injection should be on Friday 8th.

That’s it — just one week later on your usual injection day.

👉 A common misconception: some people think they need a two-week or longer break. That’s not true. In fact, leaving it too long could lead to appetite rebound and potential weight regain.

What Happens If You Get It Wrong?

• Too short a gap → you risk double dosing and higher side effects.

• Too long a gap → your appetite can surge back, making it harder to stick to your goals.

This is why it’s always best to have your switch planned with a healthcare professional.

How Ready Health Helps You Switch Safely

At our CQC-registered clinic, we take the stress out of switching:

• We create a personalised plan for your transition.

• We advise on exact timing and doses based on your medical history.

• We offer same-day prescriptions so you’re never left with a gap in treatment.

Final Thoughts

Washout periods don’t need to be confusing. Think of them as a simple reset button between treatments. By waiting the right amount of time, you keep your treatment safe, smooth, and effective.

👉 If you’re thinking about switching injections, book a consultation with our Weight Management Team. We’ll guide you step by step.