Tirzepatide

• Type 2 diabetes, with diet and exercise (Mounjaro)
• Chronic weight management in adults with obesity, or overweight with a weight-related condition (Zepbound)
• Moderate to severe obstructive sleep apnea in adults with obesity (Zepbound)

Tirzepatide is a once-weekly injection sold as Mounjaro for type 2 diabetes and as Zepbound for chronic weight management and obstructive sleep apnea. It was the first medicine to activate two gut hormone receptors at once, GIP and GLP-1, and in clinical trials it produced more weight loss than any GLP-1 medication before it. Both brands contain the same drug; they carry different FDA approvals, doses and insurance rules.

How Tirzepatide Works

After a meal, the gut releases two incretin hormones: glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). Tirzepatide is a 39-amino-acid peptide that activates both receptors. It helps the pancreas release insulin when blood sugar is high, lowers glucagon, slows stomach emptying and acts on appetite centers in the brain, so people feel full sooner and think about food less.

A fatty acid chain attached to the peptide lets it bind to albumin in the blood, which gives it a half-life of about five days and allows weekly dosing. Because the insulin effect depends on glucose, tirzepatide rarely causes low blood sugar on its own.

FDA-Approved Uses

Type 2 Diabetes (Mounjaro)

FDA approved Mounjaro in May 2022 for adults with type 2 diabetes, alongside diet and exercise. In the SURPASS trials it lowered A1c by roughly 2 percentage points at higher doses, more than semaglutide 1 mg in a head-to-head study, and most people also lost weight.

Chronic Weight Management (Zepbound)

Zepbound was approved in November 2023 for adults with obesity (BMI 30 or higher) or overweight (BMI 27 or higher) with at least one weight-related condition such as high blood pressure, type 2 diabetes or high cholesterol. In SURMOUNT-1, a 72-week trial published in the New England Journal of Medicine, average weight loss was about 15 percent at 5 mg, 19.5 percent at 10 mg and 21 percent at 15 mg, compared with about 3 percent on placebo. In SURMOUNT-5, a head-to-head trial, tirzepatide produced about 20 percent weight loss compared with about 14 percent with semaglutide, as reported in the New England Journal of Medicine.

Obstructive Sleep Apnea (Zepbound)

In December 2024, Zepbound became the first medicine approved for moderate to severe obstructive sleep apnea in adults with obesity. In the SURMOUNT-OSA trials, it substantially reduced the number of breathing interruptions per hour. It does not replace CPAP for everyone, and our sleep medicine team helps decide how the two fit together.

Dosing and How to Take It

Every patient starts at 2.5 mg once weekly for four weeks. That first dose is meant to let the stomach adjust, not to treat. The dose then rises in 2.5 mg steps no sooner than every four weeks, to a maintenance dose of 5 mg to 15 mg. Many people do well without reaching the highest dose.

Inject it on the same day each week, any time of day, with or without food, into the abdomen, thigh or upper arm. A missed dose can be taken within four days; after that, skip it. If several weeks are missed, your clinician may restart at a lower dose to avoid strong stomach side effects.

Side Effects

Stomach and bowel symptoms are the most common: nausea, diarrhea, constipation, vomiting and indigestion. They are usually worst in the days after a dose increase and fade over weeks. Eating smaller meals, stopping when full, limiting fatty and fried foods and drinking enough fluids help. Our article on managing GLP-1 side effects has practical tips.

Boxed Warning and Serious Risks

Tirzepatide carries a boxed warning for thyroid C-cell tumors, based on rodent studies; whether this applies to people is unknown. It is not used by anyone with a personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia type 2 (MEN 2). Other serious risks include pancreatitis, gallbladder disease, kidney injury from dehydration, severe allergic reactions and worsening diabetic eye disease after a rapid drop in blood sugar. Tell any surgeon or anesthesiologist that you take it, because slowed stomach emptying can raise the risk of inhaling stomach contents during sedation.

Monitoring and Follow-Up

We see patients regularly during dose increases to check weight, blood pressure, side effects and, for diabetes, A1c and home glucose readings. Kidney function, liver tests and cholesterol are rechecked at our in-office lab. As weight comes down, blood pressure and diabetes medicines often need to be reduced.

Protecting muscle matters, especially after 60. Eating enough protein and doing regular strength training help ensure that weight lost is mostly fat. Stopping tirzepatide usually leads to regaining much of the weight, so we plan for long-term use or a careful step-down.

Insurance and Cost

Coverage depends on the diagnosis. Many plans cover Mounjaro for type 2 diabetes but apply separate rules, or exclusions, for weight management, and prior authorization is common for both brands. Zepbound's sleep apnea approval can matter for coverage, because some plans treat it differently from weight loss alone. Lilly sells Zepbound vials directly to patients for a self-pay price through LillyDirect. Our staff can help you understand which product your plan covers before you start.

Compounded Tirzepatide

FDA declared the tirzepatide shortage over in late 2024, ending the period when pharmacies could make copies in large volume. FDA has received reports of dosing errors and side effects with compounded GLP-1 products, as described in FDA's concerns with unapproved GLP-1 drugs. We prescribe the FDA-approved product.

Getting Started in St. Petersburg

Our physician-led medical weight loss program uses tirzepatide, semaglutide and the newer oral options such as orforglipron when they fit your health and goals. For a side-by-side look at the two leading injections, read Ozempic vs. Mounjaro. To find out whether tirzepatide is right for you, schedule a visit.