Byetta for weight loss: does it work?

If you’ve been exploring prescription weight loss options, you may have come across Byetta. Byetta is part of a category of drugs known as glucagon-like peptide-1 (GLP-1) receptor agonists, which includes Wegovy, Ozempic, Trulicity, and other medications. Originally developed to treat type 2 diabetes by lowering blood sugar levels, these diabetes drugs can also lead to weight loss. Today, many health professionals may prescribe them for both type 2 diabetes and weight loss. 

Read on as we explore how Byetta for weight loss works and how it stacks up against other GLP-1 medications. 

Byetta (exenatide) is a prescription injectable medication that is FDA-approved to treat type 2 diabetes mellitus in combination with lifestyle changes like diet and exercise. Because Byetta also tends to lead to weight loss, it may be prescribed off-label for weight loss. Byetta mimics a hormone produced in the gut, known as GLP-1. In people with type 2 diabetes, GLP-1 medications like Byetta help the pancreas to release more insulin after you eat, thus stabilizing blood glucose levels.

GLP-1 receptor agonists also delay gastric emptying, or how quickly food leaves your stomach. By delaying gastric emptying and increasing satiation, Byetta makes you feel full sooner, so you may eat less and lose weight. In one study, Byetta delayed gastric emptying by 86 minutes, causing people to consume about 129 fewer calories per meal. 

Byetta is available in two strengths, 5 micrograms (mcg) and 10 mcg. Each pen of Byetta comes pre-filled with 60 doses. To use Byetta, you inject the medication subcutaneously (under the skin) of your thigh, abdomen, or upper arm. You inject Byetta twice a day, up to 60 minutes before your two main meals of the day (such as breakfast and dinner), as long as the injections are at least six hours apart. Typically, you will start at the 5 mcg twice-daily dose for one month, before increasing to the 10 mcg dose twice a day.

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Decreased appetite is a common side effect of Byetta. But, how much weight do people actually lose while taking Byetta? It depends.

• In clinical trials of people with type 2 diabetes, those taking Byetta lost nearly twice as much weight as those taking a placebo, losing about 6 pounds in six months.

• In a meta-analysis of obese and overweight people without diabetes, people lost nearly 10 pounds, on average, over a period of 3–6 months after starting Byetta. Their BMI also went down, and they shaved almost an inch off their waistlines.

• In a study of obese people with newly diagnosed type 2 diabetes, those taking Byetta lost nearly 13 pounds over a period of six months.

One benefit of Byetta is that you may notice weight loss as early as two weeks after starting the medication. However, it’s worth noting that the amount of weight loss achieved with Byetta can be similar to that achieved with a reduced-calorie diet. 

And, while many people lose weight with Byetta, it is not guaranteed. In a study of obese women without diabetes, about one-third of the participants lost more than 5% of their body weight within nine months. However, another third actually experienced weight gain. How much weight you lose will depend on how your body responds to Byetta and other factors, such as your diet, exercise routine, and other health conditions.

Byetta contains the same active ingredient — exenatide — as a similar medication, Bydureon BCise. Both medications improve glycemic control in people with type 2 diabetes, and both can lead to weight loss. However, they have some key differences. Let’s take a look.

Both Byetta and Bydureon BCise lead to modest weight loss, but there’s no clear winner on which produces more weight loss. In a clinical trial that compared both medications in treating type 2 diabetes, Byetta led to more weight loss than Bydureon BCise. However, other studies have found that Bydureon BCise is more effective at promoting weight loss. And, some studies have found that both medications produce similar amounts of weight loss.

Byetta and Bydureon BCise offer different pros and cons, depending on your personal medical history, weight loss goals, and preferences. Talk to your healthcare provider about which version of exenatide is the right choice for you.

Like many prescription medications, Byetta does come with some side effects. Common side effects of Byetta include:

• Nausea

• Low blood sugar (hypoglycemia)

• Vomiting

• Diarrhea

• Feeling jittery

• Dizziness

• Headache

• Dyspepsia (upset stomach or indigestion)

• Constipation

• Weakness or lack of energy

Of these, nausea is the most common side effect, affecting about one in three people taking Byetta. Fortunately, the nausea is mild to moderate for most people and tends to go away with time as your body gets used to the drug. 

Some people may be more likely to experience side effects when using Byetta. These include people with a history of pancreatitis, or kidney or gallbladder problems. People with the following conditions should not use Byetta:

• Known allergy to exenatide or any of the ingredients in Byetta 

• History of drug-induced immune-mediated thrombocytopenia from drugs containing exenatide

Because the drug delays gastric emptying, Byetta can affect your body’s absorption of other oral medications. If you are taking insulin or insulin secretagogues, like sulfonylureas, using Byetta may increase your risk of experiencing hypoglycemia (low blood sugar) — particularly in the first few weeks of taking Byetta. To reduce your risk, your healthcare provider may lower your dose of insulin. This side effect usually does not affect people who don’t have diabetes.

Additionally, people taking blood thinners like Warfarin may be more likely to experience heavy bleeding while taking Byetta. If this happens to you, stop using Byetta and contact a health professional immediately.

Serious side effects may include an allergic reaction to Byetta, or drug-induced immune-mediated thrombocytopenia, a serious condition that affects your platelet count and ability to clot blood. If you notice increased bleeding or bruising, stop using Byetta and talk to your health professional immediately if you notice increased bleeding or bruising. Some people may develop antibodies to exenatide, the active ingredient in Byetta, which may make the drug less effective in improving blood sugar levels. If this happens to you, your healthcare provider will recommend an alternative medication.

There are several weight loss medications you can take instead of Byetta, including other GLP-1 receptor agonists. For example, Wegovy (semaglutide) and Saxenda (liraglutide) are two GLP-1 medications the U.S. Food and Drug Administration has specifically approved for weight loss, although you must meet certain criteria to get a prescription for them, such as a high body mass index (BMI). 

Wegovy is injected once weekly, and Saxenda is a daily injection. When comparing those drugs to Byetta, Wegovy and Saxenda produced more weight loss. For example, after about a year of taking Saxenda in a clinical study, 2 in 3 participants lost at least 5% of their body weight. As for semaglutide, people lose nearly 15% of their body weight, on average, within about a year and a half of starting treatment.

Other GLP-1 medications produce weight loss to different extents, including Ozempic, which contains the same active ingredient as Wegovy, semaglutide. Trulicity (dulaglutide) and Mounjaro (tirzepatide) are other diabetes medications that, like Byetta, may be prescribed off-label for weight loss. 

You can also explore other FDA-approved options for weight loss. Some of these medications are approved to be used on a short-term basis (12 weeks or less). These include stimulants like:

• Phentermine

• Benzphetamine

• Diethylpropion

• Phendimetrazine

Long-term weight loss pills tend to have fewer side effects and risks than short-term options, while still promoting significant weight loss. In general, people taking these medications lose at least 5% of their body weight within one year. In addition to Saxenda and Wegovy, these include: 

• Qsymia (phentermine/topiramate)

• Contrave (naltrexone/bupropion)

• Xenical or Alli (orlistat) 

Currently, there is no generic form of Byetta. Byetta can be expensive since it is only available as a brand-name drug. On average, Byetta costs $938.32 per pen (a 30-day supply) without insurance, according to GoodRx. The price of Byetta can vary depending on your insurance coverage and the pharmacy you use. 

AstraZeneca, the makers of Byetta, offer patient assistance programs for eligible individuals to help bring down the cost of Byetta. Their Co-Pay Savings Program offers discounts for people with commercial insurance coverage, while the AZ&Me program offers discounts for people who are either on Medicare or don’t have insurance. You can learn more about these saving programs here.

If you are interested in taking Byetta, talk to your healthcare provider. Be sure to tell them about any medications or supplements you are taking, as well as any health conditions that run in your family. They can help you assess whether Byetta is a good option for you, and offer more guidance to reach your weight loss goals.

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Current version

June 21, 2023

Written by

Amelia Willson

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.