Semaglutide

Semaglutide is a prescription-only medicine that belongs to a class of drugs called GLP-1 receptor agonists. It is the active ingredient in several branded products you may have heard of: Ozempic and Rybelsus (used for type 2 diabetes) and Wegovy (used for weight management).

GLP-1 (glucagon-like peptide-1) is a hormone your gut naturally releases after you eat. Semaglutide is a long-acting copy of that hormone, so it acts on the same targets in the body but lasts much longer. In practical terms, it tends to:

• Prompt the pancreas to release insulin when blood sugar is high, which helps lower blood sugar.
• Reduce the amount of sugar the liver puts out.
• Slow how quickly the stomach empties, so food stays with you longer.
• Act on appetite signals in the brain, so many people feel full sooner and less hungry between meals.

Because it works on appetite as well as blood sugar, the same molecule can help with two different goals depending on the strength and brand prescribed. For a plain-language walkthrough of the whole class, see our guide to how GLP-1 medicines work.

Semaglutide is approved for specific medical uses, and which brand a clinician chooses depends on the goal of treatment:

• Type 2 diabetes. Ozempic (an injection) and Rybelsus (a tablet) are used alongside diet and exercise to improve blood sugar control in adults with type 2 diabetes.
• Chronic weight management. Wegovy (an injection, at a higher strength) is used together with a reduced-calorie diet and increased activity for long-term weight management in people who meet certain criteria.
• Heart protection in some people. For certain adults with type 2 diabetes and existing heart disease, semaglutide is also used to lower the risk of major cardiovascular events such as heart attack and stroke.

It is not a quick fix or a cosmetic shortcut. It is meant to be one part of a broader plan that includes food, movement, sleep and follow-up. If you are exploring options for the metabolic changes that often come with midlife, our overview of weight and metabolism puts these medicines in context. Semaglutide is not approved to treat type 1 diabetes.

Only a prescriber who knows your full history can decide whether semaglutide is appropriate for you. Broadly, it may be considered for adults with type 2 diabetes that is not well controlled, or for weight management in people who meet the approved criteria and have not reached their goals with lifestyle changes alone.

Some people should not take it. It is contraindicated if you or a close family member has had medullary thyroid carcinoma (MTC), or if you have Multiple Endocrine Neoplasia syndrome type 2 (MEN2). It should also be avoided by anyone who has had a serious allergic reaction to semaglutide.

Tell your clinician before starting if you have any of the following, because they may change the decision or call for closer monitoring:

• A history of pancreatitis or gallbladder disease.
• Kidney problems, or a tendency toward dehydration.
• Diabetic eye disease (diabetic retinopathy).
• Digestive conditions that slow the gut, such as gastroparesis.
• A history of disordered eating.
• Pregnancy, planning a pregnancy, or breastfeeding.

If semaglutide is not a good fit for you, other approaches exist. Our guide to alternatives to Ozempic and Wegovy walks through the landscape — but any switch is a decision to make with your prescriber, not on your own.

Semaglutide comes in more than one form, and it is always taken exactly as prescribed. Doses are individual: a clinician typically starts low and increases gradually over time to reduce side effects, so never copy someone else's regimen or adjust your own.

The injectable forms are usually given on the same day each week, into the stomach, thigh or upper arm, and can be taken with or without food. The oral tablet has specific instructions about taking it on an empty stomach with a small sip of water and waiting before eating or drinking anything else; your pharmacist will explain the exact routine. If you miss a dose, follow the guidance for your specific product rather than doubling up.

This page is general information only. Your prescriber and pharmacist give you the instructions that apply to you.

Most side effects are digestive and tend to appear when you first start or when the dose goes up. For many people they ease over the following weeks as the body adjusts, especially when the dose is increased slowly.

Eating smaller, lower-fat meals and stopping when comfortably full can help. Some people also report hair thinning, which is usually linked to rapid weight loss rather than the drug directly; we cover this in GLP-1 medicines and hair loss. For a fuller rundown of what to expect and when to call your clinician, see our article on Ozempic and Wegovy side effects. Tell your care team if side effects are severe, persistent, or stopping you from eating and drinking normally.

Semaglutide carries a boxed warning — the strongest warning a medicine can have. In animal studies, semaglutide caused thyroid C-cell tumors, including medullary thyroid carcinoma. It is not known whether it causes these tumors in humans, but because of this uncertainty it must not be used by anyone with a personal or family history of medullary thyroid carcinoma or MEN2. Report any neck lump or swelling, hoarseness, trouble swallowing, or shortness of breath.

Other serious risks to know about include:

• Pancreatitis. Severe, persistent stomach pain — sometimes spreading to the back, with or without vomiting — needs urgent medical attention.
• Gallbladder problems. Gallstones and inflammation can occur, more so with rapid weight loss. Pain in the upper-right belly, fever or yellowing skin should be checked promptly.
• Low blood sugar (hypoglycemia). The risk rises when semaglutide is combined with insulin or certain other diabetes pills.
• Kidney injury. Heavy vomiting or diarrhea can cause dehydration that stresses the kidneys.
• Diabetic eye disease. Rapid improvements in blood sugar can temporarily worsen diabetic retinopathy in some people.
• Serious allergic reactions. Rare but possible; seek emergency care for swelling of the face, lips or throat, or trouble breathing.

Two more points deserve emphasis. First, weight tends to return after stopping — studies show much of the lost weight can come back once the medicine is stopped, which is why it is treated as a long-term therapy rather than a short course. Second, only use semaglutide obtained through a legitimate prescription and pharmacy. Regulators have warned about compounded and counterfeit "semaglutide" products sold online or through spas, which may contain the wrong ingredient, wrong strength, or no active drug at all, and have been linked to dosing errors and harm.

Because semaglutide slows how quickly the stomach empties, it can affect how other medicines are absorbed. Share a full list of everything you take — including over-the-counter drugs, supplements and herbal products — with your prescriber and pharmacist so they can check for problems. Key cautions include:

• Insulin and sulfonylureas. Combining these with semaglutide raises the risk of low blood sugar; a clinician may adjust the plan and advise how to recognise and treat a low.
• Other oral medicines. Slower stomach emptying can change the timing or amount of drug that is absorbed, so some prescriptions may need monitoring.
• Alcohol. Can add to the risk of low blood sugar and stomach upset for some people.
• Dehydration. If vomiting or diarrhea sets in, sip fluids and let your clinician know, particularly if you also take medicines that affect the kidneys or blood pressure.

For women specifically, semaglutide is generally not recommended during pregnancy or breastfeeding, and prescribers usually advise stopping it well before a planned pregnancy. If you could become pregnant, raise this early so you can plan contraception and timing together.

None of this is a reason to start, stop or change any medicine on your own. Use this overview to ask better questions, then let your prescriber make the call that fits your health.