You have probably heard the term "GLP-1" in the news or from friends. These medicines get a lot of attention, and it can be hard to sort out what they actually are. This guide explains, in plain language, what GLP-1 medications are, how they act in the body, and why the decision to use one belongs to you and a licensed clinician.
What GLP-1 stands for
GLP-1 is short for glucagon-like peptide-1. It is a hormone your body makes on its own. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) explains that GLP-1 "targets areas of the brain that regulate appetite and food intake."
A GLP-1 receptor agonist is a medicine that acts like this hormone. Receptors are like docking sites on cells. A GLP-1 receptor agonist binds to the same receptors that natural GLP-1 uses and switches them on. MedlinePlus, from the National Library of Medicine, places these medicines in a group called incretin mimetics.
Semaglutide
Semaglutide is a GLP-1 receptor agonist. Its FDA prescribing information says semaglutide "selectively binds to and activates the GLP-1 receptor, the target for native GLP-1." The label also notes that GLP-1 is a natural regulator of appetite and calorie intake, and that GLP-1 receptors are found in several areas of the brain involved in appetite.
Semaglutide injection is sold under brand names that include Ozempic® and Wegovy®. MedlinePlus explains that it is used for several purposes, including blood sugar control in people with type 2 diabetes and, for Wegovy®, weight management in certain people. The injection is given once a week.
Tirzepatide
Tirzepatide works a little differently. It is a dual agonist, which means it acts on two kinds of hormone receptors. Its FDA prescribing information describes it as a "GIP receptor and GLP-1 receptor agonist." GIP stands for glucose-dependent insulinotropic polypeptide. Like GLP-1, it is a hormone released by the gut.
The label explains that both GIP and GLP-1 receptors are found in areas of the brain involved in appetite. It also says early, nonclinical research suggests that adding GIP may further contribute to how food intake is regulated.
Tirzepatide is sold under the brand names Mounjaro® and Zepbound®. MedlinePlus notes that it is used for type 2 diabetes and, for Zepbound®, for weight management in certain adults and for obstructive sleep apnea in adults with obesity. It is also given once a week.
How these medicines act on appetite and digestion
According to MedlinePlus and the FDA, these medicines act in a few main ways:
- Appetite signals. They act on areas of the brain involved in appetite and food intake. The FDA says Zepbound® works by activating GLP-1 and GIP receptors to reduce appetite and food intake.
- Slower stomach emptying. They slow how quickly food leaves the stomach. The tirzepatide label notes that this delay is largest after the first dose and becomes smaller over time.
- Blood sugar. MedlinePlus explains that they help the pancreas release the right amount of insulin when blood sugar is high.
Because they slow stomach emptying, both labels say these medicines may affect how your body absorbs other medicines you take by mouth. This is one reason your clinician needs to know about everything you take.
Who these medicines are approved for
For weight management, the FDA approved Wegovy® and Zepbound® for use along with a reduced-calorie diet and increased physical activity. NIDDK explains that health care professionals may prescribe weight-management medicines to adults with a body mass index (BMI) of 30 or greater, or a BMI of 27 or greater along with a weight-related health problem such as high blood pressure or type 2 diabetes. Wegovy® is also approved for some children ages 12 and older.
NIDDK notes that weight-management medicines "work best when combined with a lifestyle program." They do not replace healthy eating and physical activity.
Who should not use them
The labels for both semaglutide and tirzepatide carry a boxed warning about the risk of thyroid C-cell tumors, which were seen in studies in rodents. It is not known whether these medicines cause these tumors in people. The labels say they should not be used by people with a personal or family history of medullary thyroid carcinoma (MTC), or by people with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). They also should not be used by people who have had a serious allergic reaction to the medicine or its ingredients.
The labels also say these medicines should not be combined with other GLP-1 receptor agonists. There are other warnings as well, such as risks involving the pancreas, gallbladder and kidneys. Your clinician can walk you through them.
A prescription medicine, decided with a clinician
GLP-1 medicines are prescription medicines. Whether one is right for you depends on your health history, your other medical conditions, the medicines you take and your goals. That decision is made with a licensed clinician, not on your own.
NIDDK suggests asking your provider about any medical conditions that may raise your risk, and telling them about all the prescription medicines, over-the-counter medicines and herbal products you take. At Talvi, a licensed clinician reviews your health history before anything is prescribed.
Questions to ask your clinician
- Is a GLP-1 medicine a reasonable option for me, given my health history?
- What is the difference between semaglutide and tirzepatide for someone like me?
- Is the medicine you are suggesting FDA-approved or compounded?
- How might it interact with the other medicines I take?
- What side effects should I watch for, and when should I call you?
- What changes to eating and activity should go along with it?
The bottom line
Semaglutide is a GLP-1 receptor agonist, and tirzepatide is a dual GIP and GLP-1 receptor agonist. Both act on hormone signals tied to appetite, digestion and blood sugar. They are prescription medicines with known risks, and the choice to use one is made with a licensed clinician who knows your health history.
If you ever have severe symptoms, such as stomach pain that is severe and will not go away, or signs of a serious allergic reaction like swelling of your face or throat or trouble breathing, call 911 or seek emergency care right away.