GLP-1 Drugs: Semaglutide, Tirzepatide, and Retatrutide

Appetite and metabolic medicines

Semaglutide and tirzepatide affect appetite and blood-glucose regulation. They are ingredients in prescription medicines with specific approved uses. Retatrutide is a related drug under investigation; it does not have the same approval status.

This lesson explains the differences, evidence, and main clinical risks. Advanced growth hormone lessons and research-vial calculations are not required to understand it.

GLP-1 and GIP

Incretins are hormones involved in the body’s response to food. Two are GLP-1 and GIP. They help regulate insulin release, which affects blood glucose. GLP-1 also helps regulate appetite.

A receptor is a structure on a cell that responds to a signal. An agonist activates a receptor. Semaglutide activates GLP-1 receptors. Tirzepatide activates both GLP-1 and GIP receptors.

These medicines can reduce food intake and body weight. They also affect blood-glucose control and slow stomach emptying, which is relevant to adverse effects and other medicines. An effect on appetite does not establish that a drug is appropriate for every weight-loss goal.

Semaglutide and tirzepatide

Semaglutide is marketed under different brand names for different indications. Ozempic is a diabetes medicine; Wegovy has weight-management indications and other specified uses. A brand’s prescribing information defines its approved populations and formulation.

Tirzepatide is also marketed for different indications: Mounjaro for type 2 diabetes and Zepbound for weight management and certain patients with obstructive sleep apnea. It is often grouped with GLP-1 drugs, although it also activates GIP receptors.

Trials of these medicines have demonstrated weight reduction in the populations studied. An average trial result does not predict an individual’s response. Comparing percentages from separate trials can also mislead when populations, treatment duration, and study designs differ.

Clinical evidence concerns the medicine and formulation studied. It does not verify the contents, quality, or effects of a research-market product carrying the same compound name.

Retatrutide and research products

Retatrutide is discussed alongside these medicines because it is being investigated for weight management. An experimental drug needs its own evidence and safety assessment; being related to an approved medicine does not give it the same status.

FDA states that retatrutide is not a component of an approved drug and has not been found safe and effective for any condition. Clinical investigation is different from routine prescribing. A research vendor’s vial is not the pharmaceutical product supplied in a clinical trial.

FDA also warns that unapproved GLP-1 products sold online may contain incorrect ingredients or amounts. Compounded drugs are not FDA-approved, and the agency does not review their safety, effectiveness, or quality before marketing. These distinctions matter independently of whether the arithmetic on a vial is correct.

Clinical risks

Nausea, vomiting, diarrhea, and constipation are common adverse effects of semaglutide and tirzepatide. Symptoms can affect food and fluid intake. Severe or persistent symptoms need clinical assessment.

Their prescribing information also addresses pancreatitis, gallbladder disease, kidney injury associated with dehydration, and serious allergic reactions. Low blood glucose is a particular concern when treatment is combined with insulin or medicines that stimulate insulin release. A clinician needs the full medication list to assess interactions.

Wegovy and Zepbound are contraindicated with a personal or family history of medullary thyroid carcinoma, a particular thyroid cancer, or multiple endocrine neoplasia type 2 (MEN2), an inherited endocrine disorder. Their boxed warnings describe thyroid tumors in rodents; whether that finding applies to humans is unknown. These warnings do not mean that every thyroid condition is the same contraindication.

Severe gastroparesis, a condition in which the stomach empties slowly, is another concern in the prescribing information. Pregnancy plans, prior reactions, digestive symptoms, diabetes complications, and planned anesthesia also belong in the clinical discussion. This overview is not a complete contraindication or interaction list.

Severe persistent abdominal pain, inability to keep fluids down, or signs of a serious allergic reaction require prompt medical attention. These symptoms are not a reason to experiment with a different research product or self-adjust a protocol.

Nutrition and follow-up

Weight lost during treatment can include lean mass as well as fat. Lean mass includes more than muscle, so a change in a body-composition measurement does not directly measure muscle loss. The labels describe greater fat-mass loss than lean-mass loss; they do not promise that lean mass will be preserved completely.

Follow-up considers the treatment goal, weight trend, nutrition, adverse effects, and relevant medical conditions. Difficulty eating or drinking needs assessment rather than being treated as proof that appetite suppression is working well.

Dose increases, interruptions, and formulation changes follow the particular prescription and clinical response. This lesson does not provide a self-directed titration schedule. Different devices and concentrations can create different errors; FDA has received reports of dosing errors with compounded injectable semaglutide, including some requiring hospitalization.

Further reading

Return to Intro to peptides for the category and evidence overview. Harm reduction explains overlapping risks and the limits of monitoring.

If a prescribed formulation requires a syringe, Injection safety and Concentration and syringe math explain relevant concepts. Instructions for the actual medicine and device take precedence; a ready-to-use product does not need research-vial mixing instructions.