How do weight loss injections work?

By mimicking hormones that curb appetite and slow digestion

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Edited by: Amanda Futrell
two syringes

Weight loss injections are a popular option for those hoping to shed pounds quickly and effectively. These medications alter appetite and metabolism to help support long-term weight loss — but they come with side effects, high costs and ongoing care needs.


Key insights

Weight loss injections work by altering appetite and metabolism.

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Safety and side effects vary depending on the type of injection.

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Injections cost $1,000 to $1,500 per month, and insurance fully covers them in just 24% of cases.

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About 15% of people quit taking weight loss injections due to side effects, most of which go away over time.

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What are weight loss injections?

Weight loss injections are a newer option compared to pills, shakes and supplements. They’re popular in part because many are taken just once a week instead of daily and can be administered at home with minimal effort.

» COMPARE: 6 weight loss medication options

How do weight loss injections work?

Similar to insulin or hormonal injections, weight loss injections come in small, manageable syringes that can be inserted into the thigh, upper arm or abdomen right at home. While weight loss injections require a prescription and a doctor’s care, you don’t have to visit your doctor to use them.

Weight loss injections boost the glucagon-like peptide-1 (GLP-1) hormone, which is a naturally produced hormone in the intestines that regulates blood sugar levels, appetite and digestion. These drugs aid weight loss by curbing your appetite and helping you feel full longer.

Your body makes the GLP-1 hormone. But in people who deal with chronic obesity or Type 2 diabetes, GLP-1 hormone levels are often deficient. Weight loss injections work to boost GLP-1 levels by inhibiting hormones that often block or suppress this helpful hormone.

You might hear weight loss injections referred to as GLP-1 receptor agonists. According to Shelley Balls, a registered dietitian nutritionist with Flawless Bloom, these agonists help slow gastric emptying, promote a feeling of fullness and decrease glucose levels after eating — all of which can assist in your weight loss attempts.

Are weight loss injections effective?

Weight loss injections have been shown to be effective in clinical trials. A recent study showed that people who injected semaglutide once weekly lost nearly 15% of their body weight; those using liraglutide lost about 6%.

“These drugs have also been shown to decrease blood pressure, LDL cholesterol, triglycerides, glucose and liver fat,” Balls said. So it’s not just about losing body fat — it’s about an overall healthier body that’s at less risk of a major health crisis, like a heart attack or stroke.

Your doctor can help you determine which brand of weight loss injectable medication is right for your situation. But it’s important to remember that lifestyle changes, such as consistent exercise and healthier eating habits, are what can help sustain the weight loss that occurs from using injectable weight loss medication.

Those who pair GLP-1 drugs with regular physical activity and a well-balanced diet tend to see the best results and keep the weight off long term, Balls said.

Are weight loss injections safe?

Even though some injectable weight loss drugs are FDA-approved and have been extensively tested, Balls points out they’re still relatively new overall. As such, “I always recommend giving diet and regular physical activity 100% of your effort for quite some time before starting weight loss drugs,” she said.

The biggest risk consumers face is an increased occurrence of fraudulent and illegal selling online. “Be aware that illegally purchased weight loss drugs may be adulterated, contaminated, improperly stored and transported, ineffective or even potentially unsafe,” said Balls.

“Phrases like ‘cheap Ozempic’ and ‘no prescription needed’ are perhaps the biggest red flags when identifying fraudulent drugs. Remember if anything sounds too good to be true, it probably is,” she continued.

Phrases like ‘cheap Ozempic’ and ‘no prescription needed’ are perhaps the biggest red flags when identifying fraudulent drugs.”
— Shelley Balls, Flawless Bloom

What are the side effects of injectable weight loss medications?

Weight loss medications are effective, but they come with a long list of potential side effects you should be aware of before starting one of these drugs. While about 15% of people quit taking the drug due to side effects, most find they subside over time.

Common side effects include:

  • Bloating
  • Constipation
  • Diarrhea
  • Dizziness
  • Dry mouth
  • Excess fatigue
  • Gas
  • Hair loss
  • Headache
  • Heartburn
  • Hormonal imbalances
  • Increased heart rate
  • Insomnia
  • Nausea
  • Raised blood pressure
  • Stomach pain
  • Vomiting

How much do weight loss injections cost?

The average cost of weight loss injections at the time of publication ranges from $1,000 to $1,500 per month. According to Balls, weight loss drugs that are FDA-approved are more likely to be covered by health insurance in the future. But in many cases, insurance doesn’t currently cover the cost of these drugs.

Look for coupons or online savings programs to help lower your out-of-pocket costs.

Data from the Kaiser Family Foundation finds that only one in four people (24%) had the cost of their weight loss medication fully covered by insurance. About 20% of injection users pay the entire cost out of pocket. And since these drugs are meant for long-term weight management, the expenses can add up quickly.

Things like coupons or online savings programs can help assuage the high cost of weight loss medications. In some cases, your insurance might cover a portion of the cost, which can be helpful.

How to discuss weight loss injections with your doctor

Your doctor can help you decide if using an injectable weight loss medication is the right choice for you. It’s a good idea to come to your appointment armed with plenty of questions that can help you clearly understand everything you need to know about these drugs.

Before your visit, think through your goals for your health and your weight since these types of things can inform the conversation you have with your doctor.

Here are some helpful questions to ask your doctor before starting weight loss injections:

  • Will this drug help my specific situation?
  • How much weight can I expect to lose on this drug, and how long might that take?
  • How long will I need to take this medication?
  • Should I expect to gain weight when I discontinue this medication?
  • What sorts of lifestyle modifications should I make in order to ensure taking this drug is successful?
  • What sorts of drug interactions should I be aware of?
  • What are the side effects of this drug?
  • Are there any alternatives to taking this medication?
  • What types of things would warrant a call to your office while I’m taking this medication?

Are weight loss injections worth it?

Yes, injectable weight loss medications can be an effective way to lose significant weight, especially for those dealing with obesity. They’re easy to use and require just one dose a week instead of daily injections.

These medications often start working right away, with many people realizing benefits within the first few months. If you’re dealing with obesity, Type 2 diabetes or both, an injectable weight loss medication can have a positive impact on your overall health and wellness when combined with healthier lifestyle habits.

While weight loss injections are effective, they’re also expensive, and some people report stopping the medication due to side effects. But for those who can afford it and find that they can tolerate the drug, many say the results are worth the cost.

FAQ

What should you do if you experience side effects?

If you’re able to continue taking the drug your doctor prescribed, you may find that side effects lessen over time. Most people experience some side effects from weight loss medications — notably gastrointestinal issues like nausea, vomiting and diarrhea. However, drug manufacturers say most of these symptoms typically subside with continued use.

Be sure to ask your doctor what symptoms warrant a call to the office or an emergency room visit before you start injections.

Is it safe to use weight loss injections long-term?

While these drugs are relatively new, they’re often recommended for long-term weight management or diabetes control. Over time, clinical trials will provide more data on the safety and effectiveness of injectable weight loss medications.

How quickly can you see results from weight loss injections?

According to the Mayo Clinic, most of the weight loss from injectable weight loss medications will take place in the first four to five months of use. But you may notice changes in your appetite as early as the first week or so. Timing varies based on many factors like your weight, your individual appetite and your dosage level.


Article sources

ConsumerAffairs writers primarily rely on government data, industry experts and original research from other reputable publications to inform their work. Specific sources for this article include:

  1. The New England Journal of Medicine, “Once-Weekly Semaglutide in Adults with Overweight or Obesity.” Accessed March 26, 2025.
  2. JAMA Network, “Effect of Weekly Subcutaneous Semaglutide vs Daily Liraglutide on Body Weight in Adults With Overweight or Obesity Without Diabetes.” Accessed March 26, 2025.
  3. The New England Journal of Medicine, “Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes.” Accessed March 26, 2025.
  4. Kaiser Family Foundation, “KFF Health Tracking Poll May 2024: The Public’s Use and Views of GLP-1 Drugs.” Accessed March 26, 2025.
  5. Peterson-KFF Health System Tracker, “How do prices of drugs for weight loss in the U.S. compare to peer nations’ prices?” Accessed March 26, 2025.
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