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When does Zepbound peak in the body?

It really depends from person to person, but Zepbound usually peaks in your body around 24 hours after you take it.

For some people, it might be as soon as 8 hours, or it could take up to 72 hours.

Medically reviewed by

Craig Marsh, Clinical Reviewer

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Medically reviewed by

Mr Craig Marsh

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on Jun 19, 2025.

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Last updated on Nov 21, 2025.

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Zepbound starts working within hours, but its full effects on your appetite usually peak around Day 1 or 2.
From Day 3 to 5, its effects remain strong and consistent, with gradual tapering until Day 7.
It stays in your system for around 30 days, depending on factors like dose, metabolism, and how long you’ve been using it for.

What does Zepbound look like in the body over the course of a week?

Figure 1: Zepbound blood levels over a week after 5mg (blue), 10mg (orange), and 15mg (dark gray) doses, based on real data from people weighing over 95kg (209lb).

Immediately after injection (Day 0)

Once you take your Zepbound shot, its active ingredient tirzepatide starts working by attaching to two targets called GLP-1 and GIP receptors. But you probably won’t feel the full effects right away, as it takes a bit of time for the medication to build up in your system.

That said, some people do start noticing changes like a reduced appetite within just eight hours.

Day 1

By around 24 hours, the medication usually reaches its peak level in your blood (although this depends on the dose you’re using and your weight).

This is when you might really start feeling it, especially in your appetite. You may feel fuller after eating smaller amounts of food because Zepbound slows down how fast your stomach empties.

Day 2

For most people, Zepbound peaks on day 1 or 2.

This is when the effects are strongest. You’ll:

Likely notice fewer cravings
Feel full for longer
Have better-regulated blood sugar levels due to improved insulin release

Day 3 - 5

Zepbound concentrations decrease slightly between days three to five, but the medication remains fully active in your system. 

Effects like appetite suppression and slowed digestion continue, and stay close to the maximum effects.

Blood sugar effects and insulin function remain stabilized.

Day 5 - 7

By days five to seven, Zepbound levels continue to decrease, but the medication is still active enough to keep working. You might notice you’re a bit hungrier during these days.

Zepbound’s half-life is around 5 days.  (Half-life is the amount of time it takes for the level of a medication in your body to drop by half. So after five days, only half of the dose is still active in your body.)

Because its effects start to gradually wear off after this time, this half-life supports a weekly injection schedule.

The next weeks

After about four weeks of regular use, your body reaches something called steady-state. This is when the amount of a drug going into your body equals the amount being cleared out.

So after the first four weeks, the effects of Zepbound remain largely constant, without big ups and downs in how the medication works. Which is why, in order to allow your body to adjust, doctors typically recommend increasing the dose every four weeks.

How long does Zepbound stay in the body?

After taking a dose of Zepbound, it can stay in your system for about 30 days. That’s because it has a half-life cycle of around five days. And it usually takes five to six of these cycles (so around 25–30 days) for a medication to leave your body.

But if you’re planning to get pregnant, it’s best to wait at least two months after your last injection before trying. That’s because the drug could still be in your system, and it’s not fully known how Zepbound (tirzepatide) might affect a baby during pregnancy.

The exact amount of time Zepbound stays in your body can vary depending on a few things:

Your dose: If you’re on a higher dose, like 15 mg, you might feel the effects for a bit longer than someone taking a lower dose, like 2.5 mg.
Your metabolism: If you have a faster metabolism, your body may break it down more quickly. But if your metabolism is slower, due to things like age, genetics, or impaired liver/kidney function, it may take longer to clear.
How long you’ve been using it: The longer you’ve been on Zepbound, the more it can build up in your system, and the longer it may take for its effects to fully wear off after stopping.
Tolerance: If you’ve been taking Zepbound regularly, your body may become less sensitive to its effects over time. This is called tolerance, and it can mean the medication doesn’t feel as effective, even though it’s still in your system the same amount of time.

So while 30 days is a good estimate, it’s going to be a bit different for everyone.

And if you’re stopping Zepbound for a specific reason (like pregnancy), it’s always a good idea to talk it through with your doctor.

When are you most likely to experience side effects from Zepbound?

You’re most likely to feel Zepbound side effects like nausea, vomiting, low blood sugar, diarrhea, or constipation when you first start Zepbound or when your dose goes up. That’s because your body is adjusting to higher levels of the medication.

Our UK Clinical Lead Dr Daniel Atkinson explains:

“I often remind patients that side effects from weight loss shots like Zepbound can feel more intense if you’re dehydrated or have just eaten a large meal. Since the medication slows down how quickly your stomach empties, being too full can make you feel bloated or nauseous. Staying well-hydrated and eating smaller, balanced meals can really help reduce these effects, especially when you’re just starting or increasing your dose.”

Do different weight loss medications peak at different times in the body?

Wegovy and Zepbound are two of the most talked-about weight loss treatments right now, but they work a little differently.

That’s because they contain different active ingredients: Wegovy uses semaglutide, while Zepbound contains tirzepatide. And because of this, they peak in your system at different times.

You can read more about when Wegovy peaks in the body here.

How quickly each injection kicks in and how long the effects last can play a big role in choosing the right option for you. So if you’re weighing your options, it helps to understand how they compare.

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When we present you with stats, data, opinion or a consensus, we’ll tell you where this came from. And we’ll only present data as clinically reliable if it’s come from a reputable source, such as a state or government-funded health body, a peer-reviewed medical journal, or a recognised analytics or data body. Read more in our editorial policy.

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Disclaimer: The information provided on this page is not a substitute for professional medical advice, diagnosis, or treatment. If you have any questions or concerns about your health, please talk to a doctor.