How Long Does Semaglutide Take to Work?
Semaglutide is the active ingredient in the weight loss medicine Wegovy® and the diabetes drugs Ozempic® and Rybelsus®.
If you’re interested in a semaglutide medication for weight loss, it’s reasonable to wonder when you can expect the medicine to begin having effects on your body.
How long does semaglutide take to work? Regrettably, there’s no straightforward answer to that. You might feel changes in your appetite within a few days or weeks following your first dose and notice weight loss within a few weeks.
We’ll look at the details and share an idea of what the weight loss timeline might look like when taking semaglutide medicine.
How Long Does It Take for Semaglutide to Work for Weight Loss?
Semaglutide technically starts getting to work in the body straight away. It reaches maximum concentration one to three days after you take a dose.
You might start feeling the weight-loss-promoting effects within your first few days or weeks of treatment. These effects include:
A reduced appetite
Feeling fuller sooner and for longer after meals
Fewer cravings for unhealthy foods
Less food noise (persistent thoughts about food)
As for actual weight loss results, it can take a few weeks or longer, depending on how your body reacts and the lifestyle changes you make.
For more on early weight loss expectations, read our guide on how much weight you can lose in a week.
Weight loss your way
How Long Does Semaglutide Take to Work? What the Science Says
In clinical trials of Wegovy®, participants began losing weight within four weeks.
For example, a 2021 Wegovy® trial with almost 2,000 adults with excess weight or obesity (but not diabetes) compared the effects of 2.4 milligrams (mg) of semaglutide against those of a placebo for 68 weeks.
Trial participants were also encouraged to make healthy lifestyle changes, like eating a balanced diet with more nutritious foods and doing regular exercise.
After four weeks on Wegovy®, participants lost an average of over two percent of their body weight. After 16 weeks (about three and a half months), they had lost an average of nearly eight percent of their body weight.
Weight loss continued to progress over the next year. By week 68, participants had lost, on average, over 15 kilograms on Wegovy®.
How long it takes semaglutide to work may vary depending on your dose, how well you adhere to treatment (such as if you miss any doses), and whether you incorporate healthy lifestyle changes into your routine.
Results may also vary if you’re taking an oral form of semaglutide like Rybelsus®. But this research suggests semaglutide can start working relatively fast for weight loss.
Don’t fret if you don’t notice changes right away. Weight loss should be a slow and steady process, whether you’re taking semaglutide or not.
Semaglutide Weight Loss Timeline
There’s no set weight loss timeline when taking semaglutide. Everyone reacts to the medication differently, and many factors affect how quickly semaglutide works.
If you’d like a rough idea of what to expect, though, here’s a summary of what people lost taking a 2.4-milligram dose in the Wegovy® study mentioned above.
Time | Average Weight Loss |
Week 4 | -2% of body weight |
Week 8 | -4% of body weight |
Week 12 | -6% of body weight |
Week 20 | -10% of body weight |
1 Year | -15% of body weight |
Beyond the one-year mark, semaglutide can help you lose weight until you reach your weight loss target. After that, it can help with long-term weight management.
Your Semaglutide Options in the UK
Semaglutide belongs to a class of medicines called glucagon-like peptide-1 receptor agonists (or GLP-1s). There are a few different semaglutide drugs.
Here’s a summary of brand-name semaglutide available in the UK:
Wegovy®. Wegovy® is a weekly subcutaneous injection (meaning the needle goes into the skin, not muscle). It’s licensed by the Medicines and Healthcare products Regulatory Agency (MHRA) for weight loss in those with obesity or excess weight with a weight-related health condition. Wegovy® is available in higher doses than Ozempic®.
Ozempic®. Ozempic® is a weekly injection licensed to treat type 2 diabetes. Healthcare providers are discouraged from prescribing it for weight loss in the UK to prevent shortages.
Rybelsus®. Rybelsus® is a daily pill licensed to treat type 2 diabetes. Like Ozempic®, clinicians aren’t supposed to prescribe it for weight loss, but if you’re taking it for diabetes, you may lose weight.
Unlock your treatment plan
How Quickly Does Semaglutide Work for Diabetes?
Ozempic® and Rybelsus® (both of which contain semaglutide) are diabetes medicines that can help regulate blood glucose levels. It can take a few weeks or months for the medications to reach their full effects. This timeline may also be affected by your dose-escalation schedule — or how quickly your dose increases over time.
For example, a 2024 Ozempic® study looked at more than 2,100 participants with type 2 diabetes. They took a weekly 1-milligram dose of Ozempic® for 90 days. The average reduction in HbA1c (haemoglobin A1c), which measures average blood sugar levels, was 1.2 percent.
So, you may see improvements within the first few months of semaglutide treatment. But again, it can depend on the type and dose of semaglutide you’re taking, and it varies from person to person.
Semaglutide continues to work long-term for blood sugar control and diabetes management.
Factors Affecting How Fast Semaglutide Works
How long before semaglutide starts working? Quite a few factors can affect this:
Your biology and health profile. Everyone reacts differently to medicine and has different factors impacting how quickly or easily they can lose weight. That can include medical conditions, other medications you’re on, and genetics.
Your dose. To minimise common side effects, your GP (general practitioner) or private health provider will likely start you on a lower dose of semaglutide that gradually increases over several weeks or months. You may find that the lowest dose doesn’t do much for you, but that semaglutide begins working as your dose increases.
The form of semaglutide you’re using. Semaglutide injections may be more effective than pills for some people.
If you forget to take a dose. Don’t worry — it’s not a complete catastrophe if you forget to take a dose of semaglutide for weight loss. But it could delay how soon the medication works for you because it can take time for the drug to build up in your system.
Your lifestyle. Semaglutide works best when you make lifestyle changes, such as eating more whole foods and getting daily physical activity. The changes you make, and other lifestyle factors, can affect how effective the GLP-1 receptor agonist is. For instance, your sleep, stress levels, exercise habits, and how much of a calorie deficit you’re in can impact your weight loss progress.
What changes you’re hoping to see. The medicine starts working as soon as you take it, but it can take days or weeks before you feel the effects of semaglutide (like appetite suppression). Initial weight loss or blood sugar changes might happen after a few weeks or months, and significant changes in weight and health could take months or even upwards of a year.
Your plan is waiting
How Long Does Semaglutide Take to Work? Final Points
If you Googled “how long for semaglutide to work,“ we’ve got insight. Here’s what to bear in mind:
The key point to remember is that semaglutide starts working right away, but it can take a few weeks or months to get the full effect. That goes for appetite changes, weight loss, and diabetes management.
For weight loss, you might start to feel some effects of semaglutide (like a reduced appetite or fewer cravings) early on and then notice weight loss in your first month of treatment. Or it may take a few months before you see significant weight loss.
Either way, try not to obsess over how quickly you see semaglutide results. Focus instead on all the great steps you’re taking towards better health.
If you feel like semaglutide isn’t working for you, reach out to your GP or private provider. They may recommend a higher dose, lifestyle adjustments, a different medication, or just allowing the medication more time.
If you’re interested in Wegovy® or other weight loss injections like Mounjaro®, you can take our free online assessment to see if you’re eligible for medical weight loss treatment.
This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your GP about the risks and benefits of any treatment.