Weight Loss Injections: A Comprehensive Guide

Weight loss injections are injectable medications designed to aid in weight loss when combined with a comprehensive exercise and diet plan. These injections have gained popularity as a potential solution for individuals who have struggled to achieve their weight loss goals through traditional methods. Research indicates that semaglutide 2.4 mg (Wegovy) can lead to weight loss of up to 20 percent after one year.

How Weight Loss Injections Work

Weight loss injections, such as liraglutide, semaglutide, or tirzepatide, are generally GLP-1 (glucagon-like peptide-1) agonists. They function by mimicking the action of the naturally occurring hormone GLP-1, which is released in response to food intake. GLP-1 plays a crucial role in regulating appetite, food intake, and blood sugar levels.

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

Administration Methods

Weight loss injections are typically administered via intramuscular (IM) or subcutaneous (SubQ) injection. The specific method can vary depending on the type of injection and the healthcare provider's recommendations.

Intramuscular (IM) Injections

In this method, the medication is delivered directly into a muscle. Common injection sites include the upper arm, thigh, or buttocks. The healthcare provider will clean the injection site and insert the needle into the muscle at the appropriate angle and depth before injecting the medication.

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Subcutaneous (SubQ) Injections

Subcutaneous injections are administered just under the skin, into the fatty tissue. Common injection sites include the abdomen (around the belly button), thighs, or upper outer arm. Before administration, the healthcare provider will clean the injection site, pinch the skin to create a fold, and insert the needle at a 45 to 90-degree angle before injecting the medication.

Autoinjectors

Some weight loss injections come in pre-filled autoinjectors, which automatically deliver the medication when activated. Autoinjectors can make the injection process easier and more convenient for individuals who self-administer the injections at home.

The frequency of weight loss injections can vary depending on the specific medication and the healthcare provider's recommendations. Some injections may be administered daily, weekly, or at other intervals.

Benefits and Considerations

The benefits of weight loss injections in achieving a healthy weight often outweigh the mild to moderate side effects some individuals experience. It is important to note that weight loss injections are typically prescribed for individuals who have not been successful with diet and exercise alone and have a BMI (Body Mass Index) above a certain threshold. These injections are usually used as part of a comprehensive weight loss program that includes lifestyle changes such as a healthy diet and regular physical activity.

Types of Weight Loss Injections

Several types of weight loss injections are available, each with its unique mechanism of action and benefits.

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GLP-1 Injections

GLP-1 injections are a type of GLP-1 agonist. GLP-1 is a naturally occurring hormone that helps control hunger and keep your appetite down. GLP-1 agonists bind themselves to GLP-1 receptors and mimic the natural GLP-1 hormone, which in turn helps the body feel fuller faster and stay satisfied longer.

Tirzepatide Injections

Tirzepatide injections are considered a dual receptor agonist of GLP-1 and GIP receptors, making these injections more potent. Tirzepatide has been shown to be about 40% more powerful than GLP-1 injections, which can work well for people who need to lose lots of weight. Tirzepatide has shown remarkable effects on appetite regulation, as well as regulating blood glucose and reducing cholesterol levels.

Skinny Shots

Skinny shots contain a blend of nourishing vitamins and lipotropic compounds that help activate the breakdown of fat during metabolism in the body. These injections also contain a healthy combination of amino acids to increase energy and aid in the weight loss journey. Because skinny shots have a blend of B vitamins and other compounds, these injections offer additional benefits besides weight loss, such as helping to regulate mood, clearing mental fog, and boosting energy.

FDA-Approved Weight Loss Drugs

Most weight loss medicines are prescription only. They’re broadly classified by the way they work and can also be categorized as being a GLP-1 agonist or not. These are FDA-approved for weight management for adults as of 2025:

• Bupropion/naltrexone (Contrave®)
• Liraglutide (Saxenda®)
• Orlistat (Alli®, Xenical®)
• Phentermine/topiramate (Qsymia®)
• Phentermine (Adipex-P®)
• Semaglutide (Wegovy®)
• Tirzepatide (Zepbound®)

Bupropion/naltrexone

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.

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Liraglutide

This medication slows down how quickly your stomach empties. This makes you feel fuller for longer. Liraglutide is a daily injection. Nausea is the most common side effect.

Orlistat

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.

Phentermine/topiramate

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.

Semaglutide

This medication can also help with Type 2 diabetes because it helps manage blood sugar levels. It also helps you feel fuller for longer. It’s a weekly injection. Side effects could include stomach issues like diarrhea, vomiting and nausea.

Tirzepatide

This drug lowers blood sugar and reduces appetite by working with two natural hormones (GLP-1 and GIP) in your body. Tirzepatide helps you feel full longer, so you eat less. It’s a once-weekly injection. Common side effects include nausea, diarrhea and vomiting.

Over-the-Counter Weight Loss Medicines

Alli is the only one that’s FDA‑approved and available over the counter (OTC). Other OTC weight loss medications are supplements. They aren’t as powerful or as well-studied as prescription weight loss medications.

Comparing Weight Loss Injections

Each injection brings benefits that can help achieve weight loss goals. GLP-1 is popular among celebrities; tirzepatide has been deemed more potent than GLP-1 injections, and skinny shots can aid in weight loss but also help ensure you get a healthy dose of vitamins and their benefits.

Which Weight Loss Injection Treatment Is Right for You?

No person is the same, which means no weight loss journey is the same either! If you are thinking about weight loss injections but aren’t sure which treatment is appropriate for you, speaking to a professional will help. Many factors go into choosing a weight loss injection treatment, such as how much weight you’d like to lose, physical activity, diet, and other issues (such as mental fog, poor sleep, etc.) that you’d like to address with these injections.

Considerations and Precautions

As with any medication, side effects are possible when taking appetite-suppressing injections. Different weight loss injections are approved for different purposes. Saxenda is approved for use by adults and children ages 12 years and older, and Victoza can be used by adults and children ages ten years and older. Monjaro, Ozempic, and Wegovy can only be prescribed for adults.

You should not take liraglutide or tirzepatide if you have a history of or increased risk of thyroid cancer. Weight loss injections are available by prescription only, and healthcare professionals can administer weight loss injections for you. Having weight loss injections administered by a healthcare professional rather than self-administering the injections ensures that the correct dose is given safely each time.

Medically-supervised weight loss helps you stick to your treatment plan and reach your weight loss goals. It is important to understand the different types of weight loss injections so you get the best results. Some weight loss injections are officially approved by the Food and Drug Administration (FDA) in the United States for weight loss, and others are not officially approved for this purpose but can still be used to help you lose weight.

Additional Medications and Their Uses

• Saxenda: Can be used to help obese and overweight adults with at least one weight-related condition lose weight, as well as for weight loss in children ages 12 years and older who weigh more than 60 kg (about 132 pounds) and have obesity based on their age, height, and sex.
• Victoza: FDA-approved for the management of type 2 diabetes in people who are ten years and older. It is not FDA-approved for weight loss.
• Ozempic: FDA-approved for people who have type 2 diabetes and are at risk of cardiovascular problems. In addition to reducing appetite, Ozempic regulates blood sugar levels. Ozempic is not FDA-approved for weight loss, but it can be used for this purpose.
• Wegovy: FDA-approved for weight loss in overweight adults (those who have a body mass index (BMI) of 27-29) and at least one related comorbidity, like diabetes or hypertension, or obese adults (those who have a BMI of 30 or higher).
• Mounjaro: FDA-approved to help with blood sugar management in people with diabetes, but it can be used off-label for weight loss. Mounjaro works by slowing down the digestion process, which will help you feel full for longer periods of time.

Other Components in Weight Loss Injections

• Choline: A water-soluble vitamin that regulates energy levels and metabolism and prevents fatty acid deposits.
• Inositol: Also known as vitamin B8, helps your body use cholesterol and fat and helps with waste removal by helping fat cells leave the liver.
• L-carnitine: A naturally-occurring amino acid that provides energy and improves the function of the brain, heart, and muscles.
• Methionine: An amino acid that protects the body from free radicals that cause cell damage. Methionine also breaks down and processes fats and supports digestion.
• Vitamin B6: A water-soluble vitamin that boosts metabolism, reduces cravings, and aids in muscle growth.
• Vitamin B12: Increases metabolism, which boosts energy by stimulating your body to convert fat into energy.

The Evolving Landscape of Weight Loss Medications

The pharmacological treatment of obesity is a fast-changing landscape, and care providers must strive continuously to stay current. Before 2012, there were few weight loss medications approved by the FDA. In the 2020s, glucagon-like peptide-1 receptor agonists (GLP-1 receptor agonists) exploded in popularity and media attention. Next came a dual receptor agonist, Mounjaro, which is indicated for type 2 diabetes, and Zepbound, which is indicated for obesity.

With 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. The average weight loss varies from 5% to 21%, with some people losing more and some people losing less. Most people regain weight if AOMs are discontinued.

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. Some weight loss medications have been on the market for many years, and new ones emerge frequently. It can be easy to overlook first-generation AOMs, but these may be appropriate for some patients, especially when cost is a factor.

Specific Medications in Detail

• Wegovy: 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.
• Zepbound: 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.
• Liraglutide: 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. Side effects include nausea, diarrhea, constipation, vomiting, headache, decreased appetite, dyspepsia, fatigue, dizziness, abdominal pain, increased lipase, and renal insufficiency.
• Phentermine: 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: 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.
• Orlistat: 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.
• Setmelanotide: 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.
• 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.

Future Developments in Weight Loss Medications

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.

The Importance of a Comprehensive Treatment Plan

FDA-approved anti-obesity medications (AOMs) are safe, evidence-based therapies that target specific physiology to improve the disease and are most effective when used as part of a comprehensive treatment plan. 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. Tirzepatide is a dual GIP and GLP-1 receptor agonist that suppresses appetite, improves satiety, and supports metabolic health. In addition to impressive weight loss, studies show improvements in cardiovascular risk factors and metabolic markers.

Some medications are administered orally, and others are given as subcutaneous injections. Some patients who are less comfortable with injections may ask about weight-loss pills. There are many medications that can be obesogenic or cause weight gain. A treatment plan for obesity can comprise multiple forms of treatment, including medications, diet, exercise, and/or surgery. All weight loss medications work best in the context of a healthy eating plan and exercise. Some weight management medications are designed for short-term use and others for long-term use. Those approved by the FDA for long-term use include orlistat (Xenical, Alli), phentermine-topiramate (Qsymia), naltrexone-bupropion (Contrave), liraglutide (Saxenda), semaglutide (Wegovy, Ozempic), and tirzepatide (Zepbound, Mounjaro).

Considerations When Using GLP-1s

GLP-1s are not meant to be stopped and restarted at will. The dosing for some of these includes a long ramp-up period-up to five months-to reach full dosage. While GLP-1s have grabbed a lot of headlines, they are only the latest in a long history of evolving weight loss medications. As more physiological mechanisms for weight gain have been unearthed, drugs targeting newly discovered receptors and/or enzymes have been introduced with improved safety profiles and fewer psychological adverse events. Additionally, drugs targeting hunger or satiety signaling have been actively studied and have shown increased adoption by physicians.

As with many medications, some weight loss drugs have been on the market longer, have generic alternatives, and tend to be more affordable. GLP-1s are notoriously costly. The Kaiser Family Foundation estimates the annual net price of Wegovy at $13,600.

Addressing Weight Regain

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. Another problem with current weight loss drugs is that people tend to regain weight if they stop taking the drugs, says Dr. Hong. Some drug makers are working to address this problem. Besides helping with diabetes and weight loss, there are also some very potent anti-inflammatory benefits.

The Role of Healthcare Professionals

With prescription medications, a healthcare professional can weigh all factors affecting the patient’s lifestyle and BMI and monitor progress and side effects.

Vitamins, Supplements, and Mental Health

While no specific vitamin or supplement is considered a “treatment” for obesity or overweight, certain ones help support metabolic health. For example, studies suggest that calcium and vitamin D may play a role in regulating belly fat. Antidepressants are broken down into categories: selective serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants, monoamine oxidase inhibitors (MAO inhibitors), and others. In the SSRI group, paroxetine shows the highest associated weight gain. Weight-positive medications in the tricyclic antidepressant category include amitriptyline, doxepin, and imipramine. Bupropion (Wellbutrin), an aminoketone, is considered weight-negative and is prescribed both to assist in weight loss and to treat depression.

Guidelines and Precautions for Specific Medications

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. They can also interfere with hormonal birth control. Older AOMs also have indications based on BMI and may be contraindicated for use with certain other medications.

The Risks of Counterfeit 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.

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