Byetta is a brand-name prescription medication. It’s used with a diet and exercise program to help lower blood sugar levels (glucose) in adults with Type 2 diabetes. Byetta is not currently approved for use in children.
Byetta contains exenatide, which is a type of drug known as a glucagon-like peptide-1 (GLP-1) agonist. Byetta is given by injection.
Byetta comes in a prefilled injection pen. You use the pen to give yourself an injection under your skin (a subcutaneous injection). You inject your dose before each of your two main meals of the day (such as breakfast and dinner).
If you take Byetta, you may also be prescribed other medications such as metformin, a sulfonylurea, or both to help lower your blood sugar levels.
Byetta is effective when used on its own and when used with various combinations of diabetes drugs. It significantly lowers your hemoglobin A1c (HbA1c), which measures your average blood sugar levels over the past three months.
In one clinical study of Byetta used on its own, people receiving Byetta had a reduction in their average HbA1c levels of 0.7%–0.9% after 24 weeks. This was compared to a 0.2% reduction in people receiving a placebo (a treatment without an active drug). People receiving Byetta also had their average fasting blood sugar reduced by 17–19 mg/dL, compared with 5 mg/dL in people receiving a placebo.
Similar results were seen in other clinical studies where people received Byetta with other antidiabetic medications. These medications include metformin, a sulfonylurea (such as glipizide), a thiazolidinedione (such as pioglitazone), and insulin glargine.
The following information describes dosages that are commonly used or recommended. However, be sure to take the dosage your doctor prescribes for you. Your doctor will determine the best dosage to fit your needs.
Drug forms and strengths
Byetta comes as a prefilled injection pen. It’s available in two strengths: 5 mcg per dose and 10 mcg per dose. Each pen contains 60 doses.
Dosage for Type 2 diabetes
Your starting dosage of Byetta will likely be 5 mcg injected twice a day, in the hour before each of your two main meals. Most people give themselves one injection in the hour before breakfast and another in the hour before dinner.
However, if you don’t eat much breakfast, you could choose to have your first injection in the hour before lunch. Your second injection would still be in the hour before your dinner, as long as these meals are at least six hours apart. Ask your doctor for advice if you’re not sure when to give yourself your injections.
After four weeks, your doctor may increase your dosage to 10 mcg twice a day. This will depend on how well your blood sugar levels respond to Byetta injections. Your doctor will decide what the best dosage is for you.
What if I miss a dose?
If you forget to have your injection before a meal, don’t have it after the meal. Just leave out the missed dose and have your next injection as usual when it’s time. Never use a double dose to make up for a missed dose.
Medication reminders can help make sure you don’t miss a dose.
Will I need to use this drug long term?
Byetta is meant to be used as a long-term treatment. If you and your doctor determine that Byetta is safe and effective for you, you’ll likely take it long term.
Byetta side effects
Byetta can cause mild or serious side effects. The following lists contain some of the key side effects that may occur while taking Byetta. These lists do not include all possible side effects.
For more information on the possible side effects of Byetta, talk with your doctor or pharmacist. They can give you tips on how to deal with any side effects that may be bothersome.
More common side effects
The more common side effects of Byetta can include:
- feeling jittery
- reduced appetite
- hypoglycemia (low blood sugar; see “Side effect details” below to learn more)
Most of these side effects may go away within a few days or a couple of weeks. If they’re more severe or don’t go away, talk with your doctor or pharmacist.
Serious side effects
Serious side effects from Byetta aren’t common, but they can occur. Call your doctor right away if you have serious side effects. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency.
Serious side effects can include:
- Acute pancreatitis (inflammation of the pancreas). Symptoms can include:
- severe pain in your abdomen (belly) that won’t go away
- pain in your back
- Problems with kidney function, including kidney failure. Symptoms can include:
- urinating less than usual
- swollen ankles or feet
- fatigue (lack of energy)
- Severe allergic reaction. See “Side effect details” below.
Side effect details
You may wonder how often certain side effects occur with this drug, or whether certain side effects pertaining to it. Here’s some detail on some of the side effects this drug may or may not cause.
As with most drugs, some people can have an allergic reaction after taking Byetta. Symptoms of a mild allergic reaction can include:
- skin rash
- flushing (warmth and redness in your skin)
A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include:
- swelling under your skin, typically in your eyelids, lips, hands, or feet
- swelling of your tongue, mouth, or throat
- trouble breathing
- chest tightness
Call your doctor right away if you have a severe allergic reaction to Byetta. Call 911 if your symptoms feel life-threatening or if you think you’re having a medical emergency.
Allergic reactions to Byetta weren’t reported in clinical studies. However, mild and severe allergic reactions have been reported since the drug came on the market in 2005. It’s not clear how often allergic reactions occur.
Your blood sugar levels may fall too low while you’re taking Byetta. This is called hypoglycemia. It’s more likely to happen if you’re using Byetta with other drugs to lower your blood sugar, especially insulin and sulfonylurea drugs such as gliclazide.
- In a 24-week clinical study of Byetta used on its own, hypoglycemia occurred in 5.2% of people using 5 mcg of Byetta twice a day. In comparison, hypoglycemia occurred in 1.3% of people using a placebo (a treatment without an active drug).
- In a 30-week clinical study of Byetta used with metformin (which helps lower blood sugar), hypoglycemia occurred in 4.5% of people using 5 mcg of Byetta twice a day. Hypoglycemia occurred in 5.3% of people using placebo.
- In a 30-week clinical study of Byetta used with a sulfonylurea (which helps lower blood sugar), hypoglycemia occurred in 14.4% of people using 5 mcg of Byetta twice a day. In comparison, hypoglycemia occurred in 3.3% of people using placebo.
Talk to your doctor about what to do if you experience symptoms of hypoglycemia, which can include:
- fast heartbeat
- pale skin
- feeling weak or tired
- feeling jittery or shaky
- blurred vision
- trouble concentrating
- sudden mood changes
Pancreatitis was not reported in clinical studies of Byetta. However, a few people using Byetta have experienced acute pancreatitis (inflammation of the pancreas) since the drug came on the market in 2005. Some of these cases were serious or fatal. The exact risk of this side effect is unknown because it’s not known exactly how many people have taken Byetta during this time.
Call your doctor right away if you experience any symptoms of acute pancreatitis. Your doctor may tell you to stop using Byetta. Symptoms of acute pancreatitis can include:
- severe pain in your abdomen (belly) that may spread to your back and won’t go away
- bloated or swollen belly
Weight loss or weight gain
It’s unlikely that you’ll gain weight while taking Byetta, but you might lose weight.
- In a 24-week clinical study, people using Byetta on its own lost an average of 6–6.4 lbs. (2.7–2.9 kg). People receiving a placebo lost an average of 3.3 lbs. (1.5 kg) over the same time period.
- In a 30-week clinical study, people using Byetta with metformin lost an average of 2.9–5.7 lbs. (1.3–2.6 kg). People receiving a placebo lost an average of 0.4 lbs. (0.2 kg) over the same time period.
- In a 30-week clinical study, people using Byetta with a sulfonylurea lost an average of 2.4–3.5 lbs. (1.1–1.6 kg). People receiving a placebo lost an average of 1.8 lbs. (0.8 kg) over the same time period.
The weight loss side effect can be beneficial for people with type 2 diabetes. Weight loss is most likely caused by Byetta making you want to eat less. In clinical studies, reduced appetite was reported by 1%–2% of people treated with Byetta. However, Byetta is not a weight loss drug and should not be used solely for this purpose.
Weight gain was not reported with Byetta in these studies. Talk to your doctor if you’re concerned about gaining weight while using Byetta.
Some people using Byetta experience diarrhea. In clinical studies, diarrhea was reported in 1%–2% of people using Byetta on its own. It was reported in 13% of people using Byetta with metformin, a sulfonylurea, or both.
If you get diarrhea while using Byetta, talk with your doctor or pharmacist about how to manage it. Drink plenty of fluids to avoid getting dehydrated (when your body loses more fluid than you drink). See your doctor if you experience diarrhea that is severe or doesn’t go away.
You may find that you feel nauseated when you first start using Byetta. This is why you’ll start treatment with a low dose.
- In clinical studies, 8% of people using Byetta on its own experienced nausea and 4% experienced vomiting. In comparison, no one who received a placebo experienced nausea and vomiting.
- In clinical studies, 44% of people using Byetta plus metformin, a sulfonylurea, or both experienced nausea and 13% experienced vomiting. Of people receiving a placebo, 18% experienced nausea and 4% experienced vomiting.
Feelings of nausea tend to get better with time. Talk with your doctor if you’re still feeling nauseous after a few weeks.
While you’re using Byetta, it’s important to tell your doctor right away if you suddenly start getting new feelings of nausea along with severe stomach pain or vomiting. These could be symptoms of acute pancreatitis (see the “Pancreatitis” section above).
Hair loss (alopecia) was not reported in clinical studies of Byetta. However, it has been reported by some people using Byetta since the drug was approved.
Talk with your doctor if you’re concerned about hair loss while using Byetta.
A review of safety issues with Byetta and other drugs in the same class did not find any association between pancreatic cancer and the use of these drugs. Talk to your doctor if you’re concerned about your risk of pancreatic cancer.
Byetta hasn’t been shown to cause thyroid cancer and doesn’t have a boxed warning for thyroid cancer. However, the long-acting form of exenatide, which is the main drug in Byetta, does have such a warning. This form of exenatide is available as the brand-name drug Bydureon.
An FDA boxed warning is used to alert doctors and patients about potentially serious side effects that might be associated with a drug. Bydureon has one because it was shown to cause thyroid cancer in some animals. However, results from animal studies do not necessarily apply to humans.
The FDA has also issued boxed warnings about thyroid cancer for other medications in the same drug class as Byetta. These drugs are liraglutide (Victoza), semaglutide (Ozempic), albiglutide (Tanzeum), and dulaglutide (Trulicity). These warnings are also based on animal studies. However, these drugs have not been shown to cause thyroid cancer in humans.
It’s hard to prove whether a drug or class of drugs can increase the risk of developing any kind of cancer. This is because data needs to be collected over a very long period of time. Much more evidence is needed before experts can say with certainty if these drugs do or don’t increase the risk of thyroid cancer.
It’s worth noting that thyroid cancer is a relatively uncommon type of cancer. Talk with your doctor if you’re concerned about your risk of thyroid cancer.
To read Healthline’s complete report on Byetta, you can view it here.
Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.