Does Wegovy make you tired? Fatigue, heart rate and what to watch on GLP-1s

Short answer

Yes, Wegovy can make you tired: fatigue is a listed side effect. In the trials behind the Wegovy label, 11% of adults on Wegovy reported fatigue or weakness, compared with 5% on placebo (1). Zepbound (tirzepatide) shows the same pattern at a smaller scale: 5–7% reported fatigue, depending on the dose, versus 3% on placebo (2).

Both medicines also nudge your resting heart rate up. Wegovy raised resting heart rate by an average of 1 to 4 beats per minute more than placebo (1); Zepbound by 1 to 3 beats per minute (2). If your watch shows a higher resting heart rate in the first weeks, that matches what the labels describe.

Feeling tired on a GLP-1 isn't weakness, and you're not imagining it. Eating much less, nausea and fluid loss all add up, and you can usually see the pattern in your own data.

Note: this article is for general education and is not medical advice. Don't stop, skip or change your dose without talking to your prescriber. Get medical help right away for severe stomach pain that doesn't go away, fainting, or if you can't keep fluids down. If you have thoughts of harming yourself, call or text 988. This guide is published by Welltory, which makes one of the apps mentioned.

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What the Wegovy and Zepbound labels say about fatigue

The prescribing label is the official document the FDA reviews for each drug. Here's what the current labels report from placebo-controlled trials in adults with obesity or overweight.

Checked November 8, 2026. In the Wegovy label, "fatigue" includes fatigue and asthenia (weakness). In the Zepbound label, it includes asthenia, fatigue, lethargy and malaise. The Wegovy label says findings in the trial of Wegovy tablets were similar (1).

Two things stand out. First, some people on placebo also felt tired: losing weight, changing how you eat and simply being in a trial all play a part. Second, the extra tiredness on the medicine is real, but most people in the trials didn't report it.

What about Ozempic and Mounjaro?

Ozempic contains the same active ingredient as Wegovy (semaglutide), and Mounjaro the same as Zepbound (tirzepatide). They're approved for type 2 diabetes and have their own labels, doses and trial populations, so their numbers aren't identical. The reasons for tiredness discussed below apply to both, but check your own medicine's leaflet or ask your pharmacist for its exact side effect list.

Why GLP-1 medicines can make you tired

The labels report how often fatigue happened, not why. These are the usual suspects, and often several act at once.

You're eating much less

These medicines reduce appetite. That's the point, but a sudden drop in food can leave you low on fuel, especially if you skip meals entirely or eat very little protein. Many people notice tiredness most on days they barely eat.

Nausea, vomiting and diarrhea

Stomach side effects are the most common reactions on both drugs. They disturb sleep, put you off food and drain fluids. The labels warn that dehydration after nausea, vomiting or diarrhea has led to kidney problems in some people (1, 2).

Lower blood pressure and dizziness

As weight comes down, blood pressure often does too. Both labels list hypotension and dizziness more often than on placebo, and the Wegovy label reports fainting (syncope) in 0.8% of adults versus 0.2% on placebo (1). Feeling light-headed when you stand up can feel like tiredness. If you also take blood pressure medicine, your doctor may want to review it as your weight changes.

Low blood sugar, if you take other diabetes medicines

Both medicines can lower blood sugar. The risk is higher if you also take insulin or a sulfonylurea (1, 2). Shakiness, sweating, hunger, confusion and sudden fatigue are reasons to check your glucose if you have a meter, and to tell your prescriber.

Dose increases

Both medicines start low and step up over weeks. Some people notice that side effects, tiredness included, feel stronger in the days after a dose increase and then settle. The labels report side effects across the whole trial, not week by week, so watch your own pattern. Your prescriber decides the schedule; if a step feels too hard, tell them rather than changing it yourself.

Everything else that hasn't changed

Short sleep, stress, a cold, heavy periods, low iron and thyroid problems can all cause fatigue on their own; our guide to what fatigue is covers the common causes. Starting a new medicine makes it tempting to blame everything on it.

What happens to your heart rate on Wegovy and Zepbound

This is the part people notice on their watches before anyone mentions it.

The average change is small. Wegovy raised resting heart rate by 1 to 4 beats per minute on average compared with placebo; Zepbound by 1 to 3 (1, 2).

Some people see bigger jumps. In the Wegovy trials, 26% of adults had a resting heart rate increase of 20 beats per minute or more at some visit, compared with 16% on placebo (1). That doesn't mean it stayed that high, but it shows how much individual readings can move.

Why it matters for tiredness. A higher resting heart rate, nausea, eating less and losing fluids are all forms of strain. On a wearable, they can also show up as lower heart rate variability (HRV), the small changes in time between heartbeats, and as worse sleep scores. None of this is a diagnosis. But it explains why "I feel off and my watch says my heart rate is up" is a common combination in the first weeks.

What to look at. Compare your resting heart rate this week with your own average from before you started, not with someone else's number. Our guide to a normal resting heart rate explains typical ranges. If you train with heart rate zones, note that medicines can shift them; see how medications change your heart rate zones.

Side effect or something else? How to tell the difference

Tiredness on a GLP-1 rarely comes alone. What it travels with is often the best clue to where it comes from. This table is a starting point for a conversation with your prescriber, not a way to diagnose yourself.

What to track in your first month

You don't need a spreadsheet. A few consistent notes are enough to show whether tiredness is easing, steady or getting worse.

• Dose and date. Write down every dose step. Many questions from your prescriber start here.

• Food in plain words. "Normal", "small", "barely ate". You don't need calories to spot a pattern.

• Stomach. Nausea, vomiting, diarrhea or constipation, yes or no.

• Sleep. Roughly how long, and whether it was broken.

• Energy. A simple 1 to 5 score in the afternoon, when dips usually show.

• Resting heart rate. From your watch, or a short reading at the same time each morning.

After four weeks, read it from top to bottom. If your low-energy days line up with low-food days, that's something you can change. If they line up with dose steps, that's a conversation about the schedule. If they don't line up with anything, ask your doctor to look for other causes.

How to feel less tired on Wegovy or Zepbound

None of these replace your prescriber's advice. They're everyday basics to discuss with your care team.

1. Don't skip meals entirely. Smaller meals are fine; going most of the day on almost nothing often leads to an afternoon crash. Ask your care team or a dietitian how much protein you should aim for.

2. Drink through the day. Sip water regularly, more on days with nausea, vomiting or diarrhea. Thirst signals can be weaker when you're eating less.

3. Stand up slowly. Especially in the morning or after sitting for a while, if you feel light-headed.

4. Protect your sleep. A regular bedtime matters more when you're running on fewer calories.

5. Move gently, then build. Gentle movement, such as a short walk, is a reasonable start for many people; ask your care team what suits you. Hold off on hard workouts on days your resting heart rate is clearly above your normal and you feel drained.

6. Track around dose increases. Note the date of each step up and how you feel for the following week. Patterns make the conversation with your prescriber much easier.

7. Review other medicines with your doctor. Blood pressure and diabetes medicines may need adjusting as your weight changes. Don't change them yourself.

8. Check basics if tiredness lasts. Ask whether blood tests for iron, B12 or thyroid make sense.

Common mistakes when you're tired on a GLP-1

• Skipping or delaying doses to "get a break". Changing the schedule can change side effects in ways you don't expect. Talk to your prescriber.

• Treating very low intake as a win. Eating almost nothing usually means more fatigue, not better results.

• Pushing through hard workouts on bad days. Go lighter when your body is clearly strained.

• Ignoring fluids because you're not thirsty.

• Blaming everything on the medicine. Sleep, stress, illness and other conditions still count.

• Comparing your heart rate with a friend's. Compare with your own baseline.

Living with GLP-1 fatigue: the questions people ask next

How long does Wegovy fatigue last?

The label doesn't give a duration. Some people notice tiredness most in the first weeks and around dose increases, when stomach side effects can be strongest. If it lasts beyond that or gets worse, talk to your prescriber; something else, such as low iron or thyroid problems, may be involved.

Does Zepbound make you sleepy?

Fatigue, lethargy and malaise together were reported by 5–7% of people on Zepbound in trials, versus 3% on placebo (2). Some people describe it as sleepiness, others as heavy legs or low motivation.

Why does Ozempic make you tired?

Ozempic contains semaglutide, the same ingredient as Wegovy. Likely contributors are eating much less, stomach side effects, fluid loss and, in people who also take insulin or a sulfonylurea, low blood sugar. Check Ozempic's own leaflet for its exact side effect list.

Can Wegovy make your heart race?

It can raise resting heart rate. On average the increase was 1 to 4 beats per minute versus placebo, but some people had bigger changes at individual visits (1). If you notice your heart racing while you're resting, tell your prescriber.

Is tiredness on Mounjaro the same as on Zepbound?

They contain the same ingredient, tirzepatide, but Mounjaro is approved for type 2 diabetes and has its own label and trial data. The reasons for tiredness are similar, but people with diabetes may also need to think about low blood sugar.

Does coffee help with GLP-1 fatigue?

Coffee can mask tiredness, but it may worsen nausea or reflux for some people and can affect sleep. Water and regular meals address the likely causes of tiredness; caffeine only masks it. Ask your prescriber if you're unsure.

Before you blame yourself

When you start a GLP-1 medicine, it's easy to think: I'm finally doing something about my weight, so why do I feel so lazy? Before you blame yourself, look at what your body already recorded.

The first weeks bring real, measurable changes: far less food, sometimes nausea and fluid loss, a resting heart rate that may sit a few beats higher (1), and often lighter or broken sleep. Those are signals with a cause, not a character flaw.

Pick one lever for one to two weeks. For example: eat something with protein before noon every day, and take a reading at the same time each morning. Write one note next to each reading, like "barely ate yesterday", "nausea" or "dose step up". After two weeks, look back. You may see that your worst days follow your lowest-intake days, or that energy dips for a few days after each dose increase. Either way, you'll have something concrete to show your prescriber.

When to see a doctor

Get medical help right away for:

• severe stomach pain that doesn't go away, sometimes spreading to your back, with or without vomiting; this can be a sign of pancreatitis (2);

• fainting, or dizziness so strong you can't stand;

• vomiting or diarrhea that stops you keeping fluids down, or passing very little urine; dehydration has led to kidney problems (1);

• signs of low blood sugar that don't improve, if you also take insulin or a sulfonylurea;

• thoughts of harming yourself. The Wegovy label advises monitoring for depression and suicidal thoughts (1). Call or text 988 any time.

Contact your prescriber soon if:

• tiredness makes it hard to work or drive safely;

• your heart races while you're resting, or your resting heart rate stays clearly above your usual for more than a few days;

• pain in your upper right belly, fever or yellowing of your skin or eyes appears (gallbladder problems are listed on both labels);

• fatigue doesn't ease after the first weeks or after a dose step settles.

How to bring this up with your doctor

What to ask, by name. "Is my fatigue a side effect of [Wegovy / Zepbound], or should we check iron, B12 or thyroid?" "Should we slow down the dose increase?" "Do my blood pressure or diabetes medicines need adjusting as my weight changes?"

What to bring. Your dose schedule with dates of each increase. A short log: how much you ate, nausea, sleep, and energy. If you wear a watch, your resting heart rate before you started and now.

What to say, out loud. "Since my last dose increase on [date], I've been exhausted by mid-afternoon, and my resting heart rate has gone from about [number] to about [number]."

If you're told it's normal and will pass. Ask: "How long should I give it, and what would make you want to see me sooner?"

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How Welltory helps — and what it cannot do

The limits first. Welltory is a general wellness product, not a medical device. It doesn't diagnose side effects, tell you whether a medicine is right for you, or tell you how to change your dose. Those decisions belong to you and your prescriber.

What it can do is help you see your own pattern in the first weeks:

A morning spot reading. You can take a short HRV reading with your phone's camera and flash. It's a deliberate spot reading, not continuous monitoring, and it doesn't replace an ECG or a doctor's consultation. It doesn't work on Google Pixel phones (3). Measuring at the same time each morning makes readings comparable; see how to measure HRV without a wearable.

Data from a watch you already wear. Welltory's compatibility list marks Apple Watch and Samsung Watch for HRV measurements and activity tracking; Fitbit, Garmin, Oura and Pixel Watch are marked for activity tracking (4).

Notes on what happened in My Patterns. On iOS, when Welltory spots a stress or recovery episode and asks "What happened?", you can add a tag such as "nausea", "dose increase" or "barely ate", or describe it in your own words, so you can later see how those days compared (5).

A record to share. From the web app you can export your data as CSV to bring to your prescriber (6).

How we made it

We based this article on the FDA prescribing labels for Wegovy (semaglutide, revised May 2026) and Zepbound (tirzepatide, revised August 2026), opened on the FDA and DailyMed (US National Library of Medicine) websites. Search questions came from what people in the United States most often ask about feeling tired on Wegovy, Ozempic, Zepbound and Mounjaro. For the product section, we checked every function against the Welltory Help Center on November 8, 2026.

Made with AI tools, then edited and fact-checked by the Welltory team. See our Editorial & AI policy.

Jane Smorodnikova, co-founder of Welltory, built the methodology behind how we read physiological data.

Written by Tatsiana Yashyna.