Losing weight can be a difficult and long journey, and many have hoped for a magic weight loss pill for years. For the past few years, that pill might have come in the form of an injectable. With the rise of medications such as Wegovy and Zepbound, some might think we have found the answer. However, scientists and doctors emphasize that there is still more to come in perfecting weight loss drugs and treating obesity. Obesity and excess weight have become major health concerns worldwide, leading many individuals to search for effective, sustainable, and safe weight losing solutions. Among the various options available, weight loss injections have gained significant popularity due to their convenience and medically proven results. This article explores the different types of weight loss injections available, how they work, their effectiveness, and other important considerations. Weight loss injections are prescription-based medications administered via injection to help reduce appetite, regulate blood sugar, and promote fat loss. They are not a quick fix but rather a supportive tool for individuals struggling with obesity or weight-related health issues.
Current FDA-Approved Weight Loss Injections
Several weight loss injections are currently available, but not all are equally effective. Current approved weight loss injections include:
- Semaglutide (Wegovy or Ozempic when used for diabetes)
- Tirzepatide (Zepbound or Mounjaro when used for diabetes)
- Liraglutide (Saxenda or Victoza when used for diabetes).
A growing selection of weight loss medications available, patients may ask what the strongest or most effective weight loss prescription medication is, and which one is best for them. The answer is complicated, and newer is not always better. Determining whether someone is a candidate for weight loss medications begins with BMI. For each individual case, the doctor and patient should discuss the patient’s current health issues, other medications, and family medical history.
Semaglutide (Wegovy/Ozempic)
Semaglutide is a GLP-1 receptor agonist that mimics a natural hormone called GLP-1, which regulates appetite and blood sugar levels. Wegovy is a brand name for semaglutide, a GLP-1 receptor agonist. It was FDA-approved in 2021. It is administered as an injection and approved for use in adults and children aged 12 years or more with obesity (BMI ≥30 for adults, BMI ≥ 95th percentile for age and sex for children) or some adults with excess weight (BMI ≥27) who also have weight-related medical problems. The dose must be increased gradually over 16 to 20 weeks to arrive at the 2.4 mg dosage. This progression can help to alleviate side effects, which include gastrointestinal symptoms, headache, dizziness, and fatigue. It is intended to be used indefinitely, in combination with a healthy diet and exercise. Ozempic may be a more familiar name to some patients.
Tirzepatide (Zepbound/Mounjaro)
Tirzepatide is a dual GIP and GLP-1 receptor agonist, making it more powerful than Semaglutide in some cases. Tirzepatide is a dual GIP and GLP-1 receptor agonist that suppresses appetite, improves satiety, and supports metabolic health. Zepbound is approved to treat obesity in adults with a BMI of 30 or greater. It is both a GLP-1 and a GIP receptor agonist. Like semaglutide, it works by reducing appetite and is meant to be used in combination with diet and exercise to lose weight.
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Liraglutide (Saxenda/Victoza)
Liraglutide is a daily injectable medication that acts on hormones that send signals from the gut to the brain to make the patient feel full quicker and decrease hunger signals. Doses start at 0.6 mg to 3 mg a day. Some patients may lose 5-10% of body weight, especially with the higher dose of liraglutide. Liraglutide is also approved for Type 2 Diabetes, under the brand name Victoza.
How Weight Loss Injections Work
Weight loss drugs work in different ways to help you lose weight. Most of them work in one or more of the following ways:
- Decrease your appetite or reduce cravings
- Help you feel full
- Change how you absorb fat
- Increase how many calories you burn
- Improve insulin sensitivity
- Acting on the “weight set point” in the brain and lowering it
Semaglutide and liraglutide work by targeting one gut hormone receptor. Tirzepatide is different, because it targets two, making it a dual agonist. “Not surprisingly, when you start to target more and more of these bad hormones, the amount of weight loss achieved goes up even more,” says Kurt Hong, MD, an internal medicine and clinical nutrition physician with Keck Medicine of USC. “The next one that may get approved by the FDA is actually considered a triple agonist.” But that drug, which is being developed by Eli Lilly, is still in clinical trials and hasn’t been approved by the Federal Drug Administration, yet.
Other FDA-Approved Weight Loss Medications
Most weight loss medicines are prescription only. They’re broadly classified by the way they work. They can also be categorized as being a GLP-1 agonist or not. This is a newer class of medications that were first used to treat Type 2 diabetes. Healthcare providers noticed that it also led to significant weight loss. Because of this, some GLP-1s are now approved for weight loss, too.
These are FDA-approved for weight management for adults as of 2025:
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- Bupropion/naltrexone (Contrave®)
- Liraglutide (Saxenda®)
- Orlistat (Alli®, Xenical®)
- Phentermine/topiramate (Qsymia®)
- Phentermine (Adipex-P®)
- Semaglutide (Wegovy®)
- Tirzepatide ( Zepbound®)
Bupropion/Naltrexone (Contrave®)
Bupropion-naltrexone combines an antidepressant (bupropion) and an addiction treatment drug (naltrexone). It comes as a pill that you swallow. It works by changing your brain chemistry, so you aren’t hungry. It can raise blood pressure, so your provider will need to check yours regularly. Common side effects include nausea, headache and constipation. Bupropion also carries a suicide risk warning. This medication is also helpful if you have substance use disorder or if your main issue is sugar cravings.
Orlistat (Alli®, Xenical®)
Orlistat works by changing how your body digests and absorbs fat. A lower-dose version of orlistat (Alli) is available over the counter. It may cause side effects like gas and diarrhea. It works best when you follow a low-fat diet. These weight loss medications come in a pill you swallow. Orlistat is a lipase inhibitor that comes in a capsule. Undigested fat is then passed through the body. Some patients may lose about 5% of their body weight. An over-the-counter formulation is available at 60 mg capsules with each fat-containing meal. The only over-the-counter medicine for weight loss currently approved by the FDA is Alli (orlistat).
Phentermine/Topiramate (Qsymia®)
This combination drug helps with weight loss by decreasing your appetite and helping you burn calories. Possible side effects include increased heart rate and blood pressure, insomnia and nervousness. Phentermine as a standalone weight loss medication (Adipex-P) is for short-term use only. This medication comes as a pill you swallow. Topiramate can cause kidney stones. Phentermine is the oldest and most widely used weight loss medication. It was originally used as a short-term medication to jump-start weight loss, but now newer medical guidelines have added it to long-term therapy. Side effects include headache, overstimulation, high blood pressure, insomnia, rapid or irregular heart rate, and tremor. Topiramate can be combined with phentermine to decrease appetite and cravings. Adults with migraines and obesity are good candidates for this weight-loss medication. Some patients may lose an average of 5-10% of body weight. Daily doses with four strengths start at 3.75 mg/23 mg to 15 mg/92 mg. Side effects include abnormal sensations, dizziness, altered taste, insomnia, constipation, and dry mouth.
Naltrexone-Bupropion
Naltrexone-bupropion combines an opioid receptor antagonist with an antidepressant to affect the pleasure-reward areas of the brain and thereby decrease cravings and appetite. Start with a daily dose of one 8/90 mg tablet and gradually increase to four tablets a day. The most common side effects include nausea, constipation, headache, vomiting, dizziness, insomnia, dry mouth, and diarrhea.
Setmelanotide
Setmelanotide is a melanocortin-4 receptor agonist indicated for chronic weight management in adult and pediatric patients six years and older, with obesity due to certain rare genetic disorders.
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Plenity
A medical device rather than a medication, Plenity was FDA-cleared in 2019 for people with a BMI of 25 to 40. It consists of a capsule that releases a biodegradable, super-absorbent hydrogel into the stomach. The gel helps to increase satiety, enabling the person to eat less.
Effectiveness of Weight Loss Injections
The effectiveness of weight loss injections can vary. The average weight loss varies from 5% to 21%, with some people losing more and some people losing less.
- Tirzepatide: In the SURMOUNT-1 trial, adults with obesity or overweight (without diabetes) taking tirzepatide achieved up to 22.5% average body weight reduction at 72 weeks.
- Semaglutide: Wegovy uses 2.4mg specifically approved for weight loss, while Ozempic maxes at 1mg for diabetes.
- Liraglutide: Some patients may lose 5-10% of body weight, especially with the higher dose of liraglutide.
With Zepbound, weight loss upwards of 20%-22% of a patient’s excess body weight has been observed. Most people notice appetite reduction within days, but visible weight loss typically begins around weeks 4-8. Maximum results occur at 12-18 months. This is why developing sustainable habits during treatment is crucial.
Factors Affecting the Choice of Weight Loss Injection
The best injection for weight loss depends on each individual’s health profile and goals. At Local MD, we tailor treatment plans to meet each patient’s unique needs, ensuring safe, effective, and long-term weight management. For each individual case, the doctor and patient should discuss the patient’s current health issues, other medications, and family medical history.
BMI
The guidelines for tirzepatide (Zepbound) and semaglutide (Wegovy) state that a patient should have a BMI of 30 or a BMI of 27 with weight-related health problems. Older AOMs also have indications based on BMI and may be contraindicated for use with certain other medications. Determining whether someone is a candidate for weight loss medications begins with BMI.
Age
While some weight loss medications are FDA-approved only for adults, some-including semaglutide and liraglutide-are approved for children 12 and older with a BMI >/= 95th percentile.
Overall Health
The choice of medication should be made in consultation with a healthcare provider, considering the individual’s overall health and any existing medical conditions.
Potential Side Effects
Like all medications, weight loss injections may cause side effects. Most side effects occur early and improve over time. Side effect profiles are similar across GLP-1 medications, though individual responses vary. It’s important to follow up with a healthcare provider regularly.
- Semaglutide and Tirzepatide: Side effects include gastrointestinal symptoms, headache, dizziness, and fatigue.
- Liraglutide: Side effects include nausea, diarrhea, constipation, vomiting, headache, decreased appetite, dyspepsia, fatigue, dizziness, abdominal pain, increased lipase, and renal insufficiency.
- Phentermine: Side effects include headache, overstimulation, high blood pressure, insomnia, rapid or irregular heart rate, and tremor.
- Topiramate: Side effects include abnormal sensations, dizziness, altered taste, insomnia, constipation, and dry mouth.
- Naltrexone-Bupropion: The most common side effects include nausea, constipation, headache, vomiting, dizziness, insomnia, dry mouth, and diarrhea.
- Orlistat: It may cause side effects like gas and diarrhea.
Cost and Availability
Right now, there are two main problems for patients when using the current injectable weight loss drugs: cost and side effects, Hong says. And in terms of cost, right now there’s been a manufacturing shortage as demand has skyrocketed for these drugs. “With any medication, the longer they have been on the market, sometimes the cost will come down a little bit,” he says. Additionally, many insurance companies won’t cover the cost of these drugs for weight loss alone, without the presence of diabetes or some other comorbid condition. “It’s unfortunate, because for most people it’s not realistic in terms of pricing, but there are ways to see whether or not patients can get covered,” Hong says. GLP-1s are notoriously costly. The Kaiser Family Foundation estimates the annual net price of Wegovy at $13,600. Insurance coverage varies and will affect many patients’ choices about going on weight loss medications.
Compounded Medications
Some online healthcare providers claim to sell Ozempic, Wegovy, or Zepbound at reduced prices. However, the FDA warns against buying medications from any source other than a state-licensed pharmacy. In April 2025, they banned the sale of “counterfeit” semaglutide and tirzepatide. These medications are not made or packaged by the original manufacturers. Instead, they are compounded medications. Compounded versions of medications are made by compounding pharmacies, often to tailor a medication to specific patient needs, like an allergy to an inactive ingredient. Compounded medications are not FDA-approved. Some patients have taken these alternatives, which are generally more affordable, without ill effects. has received 520 reports of adverse events associated with compounded semaglutide and 480 reports of adverse events associated with compounded tirzepatide (as of April 30, 2025).
The Importance of Lifestyle Changes
Weight loss injections are a tool - not a cure. All weight loss medications work best in the context of a healthy eating plan and exercise. Weight-loss injections can be effective for weight loss. However, these medications don’t just help people lose weight. They also improve overall health.
Diet
Eating a balanced diet is crucial. If you're less hungry and eating less food, you need to make sure your diet still has enough of the protein, vitamins and minerals your body needs. Eat a good balance of fruits, vegetables, wholegrains, lean meat, fish, pulses, and low-fat dairy foods. If you’re eating less food while taking these drugs, you may be at risk of poor nutrition. That’s why eating a healthy balanced diet is still important.
Exercise
Staying physically active is also essential. Research shows that weight-loss injections can lead to a loss of muscle mass as well as fat.
The Future of Weight Loss Injections
With fervent consumer demand for weight loss medications, combined with rising obesity rates, more medications are bound for the market in the coming years. Pharmaceutical platform Ozmosi predicts one to two GLP-1 launches annually starting in 2026 specifically for obesity. Lilly is developing at least two new options. The first, orforglipron, is an oral GLP-1 inhibitor that completed a Phase 3 clinical trial in early 2025. It could provide a welcome alternative for people who do not want injections. Phase 3 results expected soon at 36 weeks. The other, retatrutide, targets GLP-1, GIP, and glucagon. At this writing, it is in Phase 3 clinical trials. In Phase 2, participants lost up to 24.2% of body weight at 48 weeks. Amgen is developing MariTide, a monoclonal antibody designed to increase GLP-1 receptor activity while reducing GIP receptor activity. The once-monthly injection entered Phase 3 clinical trials in March 2025. Researchers continue to study hormones that play a role in appetite for other ways to target obesity with medication. Those of interest include not only GLP-1, but also peptide tyrosine-tyrosine (PYY) and cholecystokinin (CCK). With more options available, doctors will be increasingly able to personalize treatments.
Weight Regain After Discontinuation
Another problem with current weight loss drugs is that people tend to regain weight if they stop taking the drugs. Most people regain weight if AOMs are discontinued. Some drug makers are working to address this problem. AOMs may counter the effects of metabolic adaptation and prevent weight regain. After weight reduction, the body metabolically adapts, often causing an increase in hunger hormones and a decrease in satiety hormones and resting metabolic rate, all of which can contribute to weight regain.