Weight loss injections: benefits, options, and side effects

Weight loss injections are part of a (relatively) new class of drugs called glucagon-like peptide-1 receptor agonists or GLP-1s. While many drugs in this class were initially approved to treat type 2 diabetes, they have also been approved for weight loss. 

In addition to lowering blood sugar and promoting weight loss, GLP-1 medications have other potential health benefits, including lowering blood pressure and reducing heart disease risk. 

At the same time, there are potential downsides with these medications, such as high cost, side effects, and questions about long-term use. These are all important factors to consider when talking to your healthcare provider about using these medications to lose weight.

Read on to learn more about injections for weight loss, how they work, side effects, the options available to you, and more. 

Weight loss injections are a group of prescription medications called GLP-1 receptor agonists that you inject under the skin of your abdomen, thigh, or upper arm. 

GLP-1 is a hormone in the body that stimulates the release of insulin after eating and helps lower blood sugar. It’s also an appetite hormone that slows down part of the digestive process and impacts the parts of your brain that control hunger and satiety, causing you to feel full faster.  GLP-1 medications mimic the action of this natural hormone in the body. 

There are several different GLP-1 medications currently approved for weight loss in people with obesity, including:

• Liraglutide (Saxenda)

• Semaglutide (Wegovy)

• Tirzepatide (Zepbound)

Liraglutide and semaglutide are GLP-1 receptor agonist medications, while tirzepatide is a dual GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist medication. GIP may enhance the benefits of the GLP-1 medication. 

Here’s a quick rundown of weight loss injections available in the U.S., along with details about their approved use, dosing information, and brand and generic names.

Wegovy (semaglutide)

Wegovy is a GLP-1 agonist medication that is approved to:

• Aid in weight loss for adults and children over 12 years old who have obesity, or in adults who have overweight and have a weight-related health condition (such as high blood pressure, type 2 diabetes, or high cholesterol)

• Reduce the risk of major cardiovascular events, such as heart attack or stroke, in adults who have cardiovascular disease and have obesity or overweight

Wegovy comes in a single-use pen that you inject once per week, either with or without food. With this medication, you have to take it on the same day each week. There are five different dose strengths: 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, and 2.4 mg. Your healthcare provider will typically prescribe the lowest dose first and gradually increase it over time. 

When prescribed to treat type 2 diabetes, this medication is called Ozempic. Ozempic is FDA-approved for blood sugar control in adults with type 2 diabetes. It is sometimes prescribed off-label for weight loss.

Zepbound (tirzepatide)

Zepbound is a dual GLP-1 and GIP receptor agonist  medication. It is indicated for weight management for adults who:

• Have obesity (BMI of 30 or above)

• Have overweight (BMI of 27 or above) along with a weight-related comorbid condition like high blood pressure, dyslipidemia, type 2 diabetes, obstructive sleep apnea, or cardiovascular disease

Zepbound comes in either a single-use pen or a single-dose vial that you would use with a needle and syringe. It is taken once a week, on the same day each week, with or without food. Zepbound can be injected in the stomach, thigh, or back of the upper arm, and it is recommended to rotate injection sites each week. 

Zepbound comes in different dosage amounts, ranging from 2.5 mg to 15 mg. People taking Zepbound start at the lowest dose and gradually increase it over time. 

Tirzepatide may also be prescribed for type 2 diabetes under the brand name Mounjaro. Mounjaro is approved for blood sugar control in adults with type 2 diabetes, and like Ozempic, it may be prescribed off-label for weight loss. 

Saxenda (liraglutide)

Saxenda  is a GLP-1 medication appropriate for adults who:

• Have obesity (BMI of 30 or above)

• Have overweight (BMI of 27 or above) along with a weight-related comorbid condition like high blood pressure, type 2 diabetes, or high cholesterol or triglycerides

It is also approved for children ages 12 and above who weigh more than 132 pounds and are considered obese.

Saxenda is a daily medication. It can be injected at any time of day in the thigh, abdomen, or upper arm, and can be taken with or without food. It comes in a pre-filled pen that contains 3 mL of solution; to use this drug you will need to prepare a new needle and set the appropriate dosage on the pen for each use. 

Saxenda has five dosage strengths: 0.6 mg, 1.2 mg, 1.8 mg, 2.4 mg, and 3 mg. People taking Saxenda start at 0.6 mg/day and typically increase their dose each week until they reach the maximum dosage of 3 mg daily. 

Compounded semaglutide

Compounding means that a licensed pharmacist or physician creates a medication tailored to you. Compounded semaglutide is a custom-made medication that includes a semaglutide base, the same active ingredient in  Wegovy or Ozempic.

It’s important to note that compounded medicines are not standardized or FDA-approved, so compounded semaglutide is not the same as Wegovy or Ozempic. 

Still, healthcare providers may want to prescribe compounded drugs in cases where an FDA-approved option isn’t available or may not meet the needs of a particular patient. It’s important to seek out a reputable pharmacy for compounded medications to ensure that they are safe and effective.

If you are prescribed a GLP-1  for weight loss, you will need to learn how to self-inject the medication at home. Your provider can give you tips on the best way to administer the medication, and the drug manufacturers’ consumer websites typically have instructional videos and guides. 

Be sure to read the instructions for your medication carefully, and reach out to your provider if you have any questions. 

The instructions for Zepbound, Wegovy, and Saxenda all vary slightly, but these are the general injection steps for using and disposing of a medication pen:

Collect all supplies you need for the injection so that you have them within reach. That includes the GLP-1 pen, alcohol swab, gauze pad/cotton ball, and a sharps disposable container.

1. Wash your hands with warm water and soap, scrubbing for at least 20 seconds. Dry your hands thoroughly with a clean towel. 

2. Check your pen to ensure that you have the correct dosage,  the pen has not been damaged, the medicine appears clear in the pen window, and it has not expired. 

3. Decide where you will inject the GLP-1. Options include the front of the thigh, lower stomach area (two inches away from your belly button), or upper arm. Change the injection spot each time to reduce skin irritation. 

4. Use the alcohol swab or soap and water to clean your injection site. 

5. Let your skin dry.

6. Get the pen ready: Remove the cap. 

7. Push the pen firmly against your skin to administer the dose. Note: Each manufacturer has different instructions for how to administer an injection. Be sure to read the full instructions for use.

8. Once the medication has been dispensed, lift the pen off your skin. If there is a little blood, use gauze or cotton to apply light pressure to the area.

9. Dispose of the pen properly. Ideally, use an FDA-cleared sharps disposal container, otherwise dispose of the pen in a plastic container with a tight-fitting, puncture-resistant lid.

Be sure to read the instructions for more specific information on safe storage and handling, how/when to dispose of your used pens, and specific instructions for traveling with medication. 

When combined with other lifestyle interventions, research shows that weight loss injections are effective for weight loss. 

In one trial for semaglutide, participants taking a 2.4 mg once-weekly dose lost 14.9% of their body weight over 68 weeks compared to a weight reduction of 2.4% in the placebo group. In a trial on tirzepatide, a once-weekly 15 mg dose resulted in a 20.9% reduction in body weight over 72 weeks compared to a weight reduction of 3.1% in the placebo group. 

In both trials, the treatment group paired medication with nutritional counseling, a reduced-calorie diet, and 150 minutes of exercise each week; the placebo group utilized lifestyle modifications alone. 

“This degree of weight loss is far greater than what was seen with earlier-generation anti-obesity medications and is approaching procedural and surgical level results,” says  Christopher McGowan, MD, Obesity Medicine Specialist and Founder of True You Weight Loss.

He adds that there are potential health benefits beyond the scale. “Losing more than just 10% of body weight will confer numerous downstream health benefits, like improved blood pressure, cholesterol, and blood sugar,” Dr. McGowan says. 

He points to a clinical trial published in The New England Journal of Medicine studying the impact of semaglutide in people who were diagnosed with both overweight or obesity and heart disease, but who had no history of diabetes. Those taking 2.4 mg of semaglutide weekly had a lower risk of death from cardiovascular disease, nonfatal heart disease, and stroke compared to a placebo group over the 40 months of follow-up. 

In this same trial, taking semaglutide was associated with reduced risk factors for cardiovascular disease, including blood pressure, waist circumference, lipids, and inflammatory markers. 

The exact length of time a person takes a GLP-1 medication will depend on several factors, including their weight loss goals, how well they tolerate the medication and their overall health status. 

Most healthcare providers recommend staying on these medications for one to two years to maintain weight loss.

“People will have to be on these drugs long-term or the weight will come back on,” says Charlie Seltzer, MD, a board-certified obesity medicine doctor in Philadelphia.

Dr. McGowan adds that clinical trials for semaglutide also demonstrate this. “Patients regained roughly two-thirds of the weight they lost within one year of stopping the treatment. Over time, most patients will regain all the weight they lost, or more, after discontinuing treatment,” he says. 

Dr. McGowan says this is likely due to genetic and physiological mechanisms driving excess weight, adding that when stopping these medications, people experience a rapid return of their hunger. 

“Weight is not a result of willpower,” Dr. McGowan says. “While continued exercise and healthy eating can help to slow this process, it can’t prevent the inevitable.” He adds that some people say they feel even hungrier or overcome by stronger “food noise” than they experienced before starting weight loss medication. 

If you are interested in GLP-1 medicine, keep in mind that this is designed as a long-term treatment.

The most common side effects of GLP-1 medications include:

• Nausea

• Bloating

• Diarrhea

• Constipation

• Vomiting

• Loss of appetite

Other side effects may include dizziness, abdominal pain, headaches, indigestion, or injection site reactions such as pain, itching, or redness.

These side effects typically occur at the start of treatment and when switching to a higher dosage but tend to improve with time. If you’re concerned about side effects, talk to your provider about managing your dose, which includes starting at the lowest dose and increasing it slowly over time

“While side effects are a big concern for the GLP medications, most people find that side effects are manageable,” says Sarah Stombaugh, MD, a family medicine physician and a diplomate of the American Board of Obesity Medicine. 

To help manage side effects, Dr. Stombaugh recommends eating small meals with each dose, staying hydrated, making sure you’re taking in electrolytes, and consuming protein shakes to ensure you’re getting some nutrition even if you don’t have much of an appetite. 

She also recommends starting a fiber supplement at the same time with a GLP-1 to prevent constipation. If regularity continues to be a problem, your provider may advise taking a stool softener or laxative. 

Warnings and precautions 

Severe adverse effects are rare, but may include:

• Acute (sudden) pancreatitis or inflammation of the pancreas, the organ that makes insulin and digestive juices

• Increased heart rate

• Gallbladder issues, such as inflammation or gallstones

• Gastroparesis, a condition that affects the muscles and nerves in the stomach and slows down food digestion 

Some populations may experience complications or risks with these medications. For example, in a clinical trial for Wegovy, 4% of adults who have type 2 diabetes and a BMI over 27 (considered overweight) developed diabetic retinopathy, a potential complication of diabetes that leads to blood vessel damage in the retina. 

Although rare, an allergy to these medications is also possible. Trials on Zepbound found that 0.1% of patients had a severe hypersensitivity reaction (such as anaphylaxis) compared to 0% in the placebo group. 

This is not an exhaustive list of all potential side effects or complications of these medications. If you’re considering medication for weight loss, the first and most important step you can take is to connect with a provider for a medical consultation to discuss these risks in detail. 

During your consultation be sure to share as much information as possible about your unique health history, family history, current medications, and known health conditions and allergies to find out if you are a good candidate for these medications, or if there are any concerns regarding complications. 

Ask how your health is monitored while on these injections, how to help minimize common side effects, and about warning signs or any symptoms that require immediate medical attention. 

If your provider determines that you’re a good candidate for weight loss medication, they will have you start at the lowest dose, and then gradually increase your dose over time. Depending on the medication and how well you tolerate it, they may increase your dose each week or every four weeks. This approach can help your HCP monitor your progress and can also help to minimize potential side effects.

Each of these medications comes with eligibility criteria, but these drugs are generally indicated for:

• Adults who have obesity (BMI of 30 or above)  

• Adults  who have overweight (BMI of 27 or above)  as well as a weight-related comorbid condition, such as high blood pressure, type 2 diabetes, and obstructive sleep apnea

Some groups of people should not take these medications, including:

• People who are pregnant

• People with a personal or family history of medullary thyroid cancer

• People who have a known serious hypersensitivity to the ingredients in the medication

Additionally, you should not use these medications in combination or with other weight loss medications.

There may be other reasons why these medications are not right for you, including if you have severe side effects or certain underlying health conditions. For some people, other treatments, including oral weight loss drugs, are a better option. That’s why it’s important to discuss your weight loss goal, personal and family medical history, and any side effects with your provider.

Weight loss injections are expensive. Factors like insurance, coupons, and manufacturer savings cards can reduce that price. 

Without insurance, Wegovy and Saxenda each cost $1,349.02 per month. However, if your insurance covers weight management medications, you may pay less than that. Some drug manufacturers also have special savings or cash payment options. For example, Zepbound has a self-pay option without insurance: $399 per month for the starting 2.5 mg dose. Once you increase to the higher 5 mg dose, you’ll pay $549 per month. 

To know exactly how much you can expect to pay, contact your insurance company to discuss your benefits and eligibility requirements, and ask if you will need a prior authorization form. In some cases, insurance may fully cover weight loss medication, reducing your cost to $0. 

Keep in mind that insurance coverage will vary by plan, and some plans may not cover these medications if they are being used off-label. 

While GLP-1s  have been hyped as miracle cures, there is no magic wand for weight loss. These medications are designed to be paired with diet and exercise to achieve significant and sustainable weight loss. 

In clinical trials, participants ate in a calorie deficit (consuming around 500 fewer calories per day) and exercised for about 150 minutes per week.  

“Studies show that patients who use GLP medications alongside intensive lifestyle modifications have more significant weight loss compared to people who used medications alone,” says Dr. Stombaugh. 

She advises people using weight loss drugs to eat a protein-rich diet and participate in regular physical activity, including resistance exercise. These two measures have been shown to help preserve muscle mass and strength in people with obesity during weight loss, per research in Nutrients.

Semaglutide, liraglutide, and tirzepatide are all FDA-approved medications for weight loss. This means they have been evaluated for safety and efficacy in clinical trials.

Whether or not they’re safe for you depends on your personal medical and family health history. These medications require a prescription, and it’s important to take them under the guidance of a medical provider.

For the best — and safest — results, you’ll want to discuss any current and past health conditions as well as your family health history to determine if your risk for using these medications outweighs its possible benefits. 

• GLP-1 receptor agonist medications such as Wegovy, Saxenda, and Zepbound are FDA-approved for weight loss.

• This class of drugs mimics the effects of the GLP-1 hormone, which helps to curb appetite, lower blood sugar, and help you feel full faster. 

• In addition to weight loss and blood sugar control, these medications may also decrease cardiovascular risks in certain groups of people. 

• When paired with a reduced-calorie diet and regular exercise, research shows that these medications are effective for weight loss – clinical trial participants reported a 15-20% reduction in body weight.

• These drugs are meant to be taken long-term, and stopping them too soon may result in rebound weight gain. 

• The most common side effects include diarrhea, nausea, and constipation. Severe side effects are rare, but you should always speak with a provider to understand your risk. 

Talk to a knowledgeable healthcare provider to determine if these medications are right for you, and if so, which one is best suited to your health needs and weight loss goals. They can also provide guidance on managing common side effects and change the dose or type of medication if needed. 

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Current version

November 15, 2024

Written by

Jessica Migala

Fact checked by

Nesochi Okeke-Igbokwe, MD, MS

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About the medical reviewer

Nesochi Okeke-Igbokwe, MD, MS

Nesochi Okeke-Igbokwe, MD, MS, is a physician, health expert, media contributor, and health writer based in the New York City area. She’s a practicing internist as well as a civil surgeon designated by the United States Department of Homeland Security and the United States Citizenship and Immigration Services.