What is Tirzepatide? How it Works, Dosages, and Side Effects

What is Tirzepatide? How it Works, Dosages, and Side Effects

Table of Contents

I. What is Tirzepatide?

II. How Does Tirzepatide Work?

III. Tirzepatide Dosages

IV. Tirzepatide Side Effects

V. Tirzepatide for Weight Loss

VI. Conclusion

Tirzepatide is one of the newest medications available to help with weight loss and type 2 diabetes. FDA-approved in 2022 under the brand name Mounjaro, tirzepatide is an injectable medication used to improve blood sugar control in adults with type 2 diabetes. 1 More recently, it was also FDA-approved under the name Zepbound to aid in weight loss for people with obesity or who are overweight. 2

In this article, we will provide a comprehensive overview of tirzepatide. We will explain what it is, how it works in the body, dosing information, potential side effects to be aware of, and the research behind its effectiveness for weight loss

What is Tirzepatide?

The Food and Drug Administration (FDA) has approved two new medications containing tirzepatide:

  • Mounjaro is a once-weekly injection used to lower blood sugar in adults with type 2 diabetes. It was approved by the FDA in May 2022. 1
  • Zepbound, a once-weekly injection, was approved in November 2023 as a treatment for chronic weight management in adults with a BMI of 30 or higher, or those with a BMI of 27 or more along with at least one weight-related complication such as high blood pressure, type 2 diabetes, obstructive sleep apnea, or cardiovascular disease. 2

What makes tirzepatide unique is its dual mechanism of action on GIP and GLP-1 receptors. This dual action provides greater improvements in blood sugar and weight compared to similar medications like semaglutide that only activate GLP-1. 3

Studies have demonstrated that tirzepatide offers substantial health benefits:

  • HbA1c: Tirzepatide 15 mg decreased HbA1c levels by 2.3% over 40 weeks.
  • Weight loss: Tirzepatide 15 mg resulted in a weight loss of 5.5 kg (12.1 lbs) over 40 weeks. 4

How Does Tirzepatide Work?

Tirzepatide stands out from other diabetes and weight loss medications because it combines two different classes of drugs. Specifically, tirzepatide is a dual glucagon-like peptide-1 (GLP-1) receptor agonist and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist. This unique approach provides enhanced blood sugar control and weight loss. 3

GLP-1 and GIP are incretin hormones released after eating that help regulate blood sugar. Tirzepatide was designed to mimic these natural effects:

  • It stimulates the pancreas to produce more insulin when blood sugar is high. This allows cells to absorb excess glucose from the bloodstream.
  • It reduces glucose production by the liver between meals. This prevents blood sugar spikes when fasting.
  • It promotes feelings of fullness and slows stomach emptying. This supports portion control and weight management. 3

Tirzepatide Dosages

Tirzepatide is a once-weekly injection that comes in six different dosages to allow for gradual dose increases. The pre-filled pens contain the following amounts of tirzepatide:

  • 5 mg
  • 5 mg
  • 5 mg
  • 10 mg
  • 5 mg
  • 15 mg 3

To take your dose, inject the medication under the skin (subcutaneously) in your abdomen, thighs, or upper arms. Tirzepatide can be injected at any time of day, with or without food. 3

When you first start taking tirzepatide, your doctor will have you begin at a low dosage and gradually increase it over the first couple of months. This gradual increase allows your body to adjust to the medication. 3 A typical starting schedule would be:

  • Month 1: Your doctor will start you on 2.5 mg injected once weekly. This initial dose is too low to have any significant health effects but allows your body to get accustomed to the medication.
  • Month 2: Your dose will increase to 5 mg once weekly.
  • After month 2: If a higher dose is needed for your treatment, your doctor will increase your dosage in increments of 2.5 mg at a time, waiting at least four weeks between increases. 3

The FDA recommends maintenance dosages of 5 mg, 10 mg, or 15 mg injected once weekly. 3 Your doctor will work with you to determine the dosage that is most effective for you.

Tirzepatide Side Effects

a woman experiencing stomach pain

While tirzepatide is generally well-tolerated, some side effects may occur as your body adjusts to the medication. The most common side effects are:

  • Nausea
  • Diarrhea
  • Vomiting
  • Constipation
  • Abdominal pain
  • Upset stomach
  • Injection site reactions
  • Fatigue
  • Burping
  • Hair loss
  • Gastroesophageal reflux disease (GERD) 3

These symptoms are often mild and tend to subside as your body gets used to tirzepatide. However, if they persist or get worse, be sure to contact your doctor for guidance. They may be able to provide tips for managing side effects or adjust your dosage if needed. 3

In rare instances, more serious side effects can occur on tirzepatide. If you experience any of the following, contact your healthcare provider immediately:

  • Severe gastrointestinal disease
  • Acute kidney injury
  • Acute gallbladder disease
  • Acute pancreatitis
  • Allergic reactions
  • Low blood sugar (hypoglycemia)
  • Diabetic retinopathy complications in patients with type 2 diabetes
  • Suicidal behavior and ideation 3

Tirzepatide for Weight Loss

a person weighing themselves on a scale

Tirzepatide promotes weight loss by reducing appetite and promoting the feeling of fullness, leading to a decrease in calorie intake. 3

Since tirzepatide mimics two hormones involved in controlling hunger and satiety (GLP-1 and GIP), its effects tend to be stronger than medications like semaglutide that only target one hormone (GLP-1). 3

Clinical trials have found that tirzepatide can lead to meaningful weight loss, with the amount of weight lost depending on the dosage. 5 In a 72-week study of 2,539 overweight or obese participants without diabetes, researchers found promising results:

  • Participants receiving tirzepatide 5 mg lost 16.1 kg (35.5 lbs.)
  • Participants receiving tirzepatide 10 mg lost 22.2 kg (48.9 lbs)
  • Participants receiving tirzepatide 15 mg lost 23.6 kg (52 lbs.) 5

It's important to note that the participants in this study also made healthy lifestyle changes to support their weight loss while taking tirzepatide. These changes included:

  • Regular counseling from a dietician on balanced eating
  • Maintaining a moderate daily calorie deficit of 500 calories
  • Getting 150 minutes per week of physical activity 5

Conclusion

Tirzepatide is an exciting new weight loss medication. Clinical trials have shown it to be even more effective for weight loss than semaglutide. For those looking to lose a substantial amount of weight, tirzepatide could be a promising solution.

However, as with any medication, it is important to talk to your doctor to find out if tirzepatide is suitable for you. Your doctor can review your medical history and symptoms and decide on an appropriate weight loss treatment.

References

  1. FDA Drug trials snapshots: Mounjaro
  2. FDA FDA approves new medication for chronic weight management
  3. FDA Zepbound
  4. Frías, J. P., Davies, M. J., Rosenstock, J., Pérez Manghi, F. C., Fernández Landó, L., Bergman, B. K., Liu, B., Cui, X., & Brown, K. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes
  5. Jastreboff, A. M., Aronne, L. J., Ahmad, N. N., Wharton, S., Connery, L., Alves, B., Kiyosue, A., Zhang, S., Liu, B., Bunck, M. C., & Stefanski, A. Tirzepatide once weekly for the treatment of obesity