Trying to lose weight quickly can feel like an uphill battle, but weight loss medications like Ozempic or Wegovy can speed up the process. If you're considering one of these, you might be wondering: How fast does semaglutide work? And when will the number on the scale realistically start to change?
The answer to that question depends on a number of factors, from your genetics to your age to your sex. But, for most people, effects of semaglutide medications show up faster than you’d think. People can lose on average anywhere from five to 20 percent of their weight on these drugs in one year, depending on their starting point, research has found. But, before you make it to that one year mark, when is the earliest you’ll start seeing results? Will you notice changes in a week, or how about in four weeks, when you’re typically eligible to increase your dose?
Ahead, an endocrinologist breaks down when you can expect to see a change on semaglutide—and the factors that may slow down or speed up its effects.
Meet the expert: Rekha Kumar, MD, is an endocrinologist at New York-Presbyterian and Weill Cornell Medicine.
Semaglutides 101: A quick refresher
Semaglutide medications first hit the market to treat diabetes, but more recently, they’ve been used for weight loss. Semaglutide meds are part of a class of glucagon-like peptide-1 (GLP-1) receptor agonist drugs. They mimic a hormone you already produce in your body that signals fullness, says Rekha Kumar, MD, an endocrinologist at NewYork-Presbyterian and Weill Cornell Medicine.
The GLP-1 hormone is released naturally in your intestines after you eat a meal, which stimulates insulin production, lowers your blood sugar, and tells you you’re full. This synthetic version does the same—but it actually lasts longer, which means you get fuller easier and stay satiated for longer as well, Dr. Kumar adds.
Decreased appetite and reduced cravings contribute to weight loss on semaglutide, according to a 2021 study published in Diabetes, Obesity, and Metabolism. Semaglutide can be an effective way to lose weight; people categorized as overweight or obese were able to lose 5.9 percent of their body weight in three months on semaglutide and 10.9 percent in six months, according to a 2022 study published in JAMA Network Open. And, you actually might see some small amounts of weight fall off as early as one week in, says Dr. Kumar.
How long does it take for semaglutide to kick in?
Semaglutide medications are typically injections taken once a week, and you might start to notice effects as soon as that first dose, says Dr. Kumar. “Patients will begin to see the effect potentially in the first week, but likely within the first four weeks,” she says. “Everybody is different, but that is the range.”
During those early weeks on semaglutide, you might experience increased fullness or getting fuller easier, not thinking about food as much, and overall eating less. For example, a meal that you’d previously finish with no problem might leave you with leftovers for tomorrow, says Dr. Kumar. You also might experience some mild side effects like nausea, but those will likely pass in coming days, she says.
When it comes to weight loss, people on semaglutide typically lose anywhere between half a pound to two pounds per week, says Dr. Kumar. The amount of weight you lose depends on many factors, including your starting point, other medications you’re taking, and more.
Certain factors can impact how quickly semaglutide works.
Like any med, results aren't one-size-fits-all, so the timing of your results will probably differ from your friend's. Here are some of the factors that can impact your weight loss on semaglutide, according to Dr. Kumar.
Metabolism
Conditions like fatty liver disease, diabetes, and high blood sugar can make weight loss more complex because there is already some level of metabolic dysfunction, says Dr. Kumar. These conditions tend to come with more severe insulin resistance so they can be harder to or take longer to treat, she says. As as a result, you may see less of an initial dramatic effect of medicine, or it may impact the speed at which semaglutide works for you.
Age
As you age, your metabolism slows, which may play a role in how quickly semaglutide works in your body. It's very common for weight gain to start during perimenopause, a few years before menopause, per Mayo Clinic. For many women, this can start in their 40s, and weight gain often continues at about the rate of 1.5 pounds each year throughout their 50s, per Mayo Clinic. After 60, your metabolism starts to decline by less than one percent per year, according to a 2021 study published in Science.
Perimenopause and Menopause
Menopause might decrease how fast you are able to lose weight, says Dr. Kumar, but semaglutide should still help with other symptoms, like sugar cravings, earlier on.
Biological Sex
Women might be more likely to lose more weight on semaglutide medications than men, according to a 2024 study published in JAMA Network Open. This could have to do with differences in hormones, which play a big role in weight loss, or the fact that women tend to be smaller than men, according to experts. It also could be because women tend to have more body fat, and therefore have more to lose in the first place—or that they tend to be more insulin resistant, adds Dr. Kumar.
Other Medications
Certain chemotherapies, steroids, hormonal medications like anti-estrogen treatments, antidepressants, or antipsychotics are known to cause weight gain. This means you may not see as much weight loss on semaglutide as you would without taking those drugs, says Dr. Kumar.
Treatment Plan and Dosage
The higher the dosage of semaglutide you’re on, the more significant the impact (and potential side effects) you will see. The dosage doesn't necessarily influence when the onset of side effects will occur—but mainly, their severity. A higher dose doesn’t always mean better results. To be safe, work with your doctor to find the most tolerable level for you.
Genetics
Your genetics will also impact how effective and how responsive you are to semaglutide, and this is true for all medications, says Dr. Kumar.
Lifestyle Factors
Semaglutide works best for weight loss for people who use it in addition to lifestyle and diet modifications, says Dr. Kumar. This includes exercising (which can also help maintain muscle mass, which can be negatively impacted by the drug) and eating healthy, well-balanced meals.
Olivia Luppino
Editorial Assistant
Olivia Luppino is an editorial assistant at Women’s Health where she covers health and fitness. She previously wrote for The Cut, POPSUGAR, and Salon and has written about everything from New York Fashion Week to dating app trends to the United States Women’s National Soccer team (a.k.a. her heroes). When she isn’t writing, Olivia is likely catching up on Bravo shows or running late to barre class.
