What You Need to Know Before Taking Weight Loss Pills

A lot of people are talking about weight loss pills right now. Before you take any, it helps to understand what they actually do, who they are for, and what tradeoffs you are accepting when you start them.

Below, you will find a clear overview of how prescription weight loss medications work, the benefits doctors see in research, the risks and side effects you need to know about, and practical questions to ask your provider before you decide.

Understand what “weight loss pills” really are

When you hear “weight loss pills,” you might think of everything from late-night TV supplements to FDA approved prescription medications. These are not all the same.

Most experts divide weight loss medications into two broad groups:

Prescription medications that your healthcare provider prescribes for obesity or overweight with health complications
Over the counter products and supplements that you can buy on your own without medical supervision

The research you see in the news almost always refers to prescription medications, not herbal blends or “fat burners.”

As of 2025, prescription medications approved by the U.S. Food and Drug Administration (FDA) for adults include combinations like bupropion naltrexone, phentermine topiramate, and drugs like liraglutide, semaglutide, tirzepatide, and orlistat. Each works in a different way, such as reducing appetite, helping you feel full sooner, or blocking some fat absorption in your intestines (Cleveland Clinic).

Over the counter remedies, on the other hand, are generally not recommended by major medical centers due to limited evidence and the potential for serious side effects. You are advised to talk with your provider before you try any of those products on your own (UC Davis Health).

If you are thinking about “weight loss pills,” you will want to be very clear that you are looking at evidence based, FDA approved options and that you are using them under medical supervision.

Learn who weight loss pills are for

FDA approved weight loss medications are not meant for everyone who wants to lose a few pounds. They are usually reserved for people who meet specific health criteria.

You may be a candidate if:

Your body mass index (BMI) is 30 or higher, which falls in the obesity range
Your BMI is 27 or higher and you also have a weight related condition such as high blood pressure, type 2 diabetes, or high cholesterol

This is the basic guidance from the Mayo Clinic and other major health systems (Mayo Clinic, UC Davis Health).

You would usually not take these medications if you are:

Pregnant, planning to become pregnant soon, or breastfeeding
Under 18, unless a specific drug is approved in that age group and prescribed by a specialist
Someone with certain medical conditions that interact poorly with a given drug, such as uncontrolled high blood pressure or heart disease in the case of some stimulant medications

Your provider will review your full medical history and current medications before deciding whether a weight loss pill is a safe option for you.

Know how much weight you might actually lose

Weight loss pills are often marketed with dramatic before and after images, but the realistic, research based results are more moderate and more varied by drug.

Across medications, most adults can expect to lose about 3 percent to 12 percent of their starting body weight over one year, on top of what they would lose from healthy eating and regular physical activity alone (Mayo Clinic, Cleveland Clinic). Many people see around 5 percent weight loss within three to six months.

Some of the newer medications, especially the GLP 1 and dual agonist drugs, have shown higher averages in clinical trials:

Semaglutide (Wegovy), a GLP 1 receptor agonist, helped adults lose about 14 percent of their starting weight on average in pill form, and up to 17 percent with 15 months of use combined with diet and exercise (GoodRx)
Tirzepatide (Zepbound), a dual GLP 1 and GIP receptor agonist, has produced up to 22.5 percent average weight loss at 72 weeks in adults with obesity or overweight without diabetes in the SURMOUNT 1 trial (Obesity Medicine Association)

Older medications tend to produce more modest changes. For example:

Phentermine alone typically helps people lose about 3 percent to 5 percent of their initial weight and is only FDA approved for short term use, usually up to 12 weeks, because of heart related safety concerns (GoodRx)
Contrave (bupropion naltrexone) has helped more than 40 percent of adults lose at least 5 percent of their initial weight after one year in early studies, and over 20 percent lose at least 10 percent (GoodRx)

Your results will depend on the specific medication, your starting weight, your health conditions, and how consistently you are able to stick with lifestyle changes alongside the drug.

Understand the health benefits beyond the scale

You might be most focused on the number on the scale, but the main reason doctors are interested in these medications is the effect on your overall health.

Even a modest weight loss of 5 percent to 10 percent of your starting weight can help:

Lower blood pressure
Improve blood sugar control
Reduce triglyceride levels

Prescription weight loss drugs can help you lose 3 percent to 12 percent more total body weight than lifestyle measures alone over a year, which can significantly amplify those improvements in blood pressure, blood sugar, and blood fats (Mayo Clinic).

For people at high risk of type 2 diabetes or heart disease, these changes can be especially important. This is part of why GLP 1 agonists like Wegovy, Zepbound, and Saxenda are now considered some of the most effective and clinically meaningful options available for weight management (UC Davis Health).

Recognize that medication is not a standalone fix

Even with strong medications, you are not off the hook when it comes to how you eat and move.

All major medical organizations emphasize that weight loss pills are meant to be an addition to lifestyle changes, not a replacement. You are expected to follow a balanced, reduced calorie eating plan, increase your activity level, and work on sleep, stress management, and other habits that affect your weight (Mayo Clinic).

This matters for two reasons:

You typically lose more weight when you combine the medication with healthy habits than with the pill alone.
Those habits are what help you keep the weight off if your doctor ever reduces your dose or stops the medication.

In fact, many people regain at least some weight after stopping prescription medications. The Mayo Clinic notes that healthy lifestyle habits can help limit how much you regain (Mayo Clinic).

With drugs like semaglutide, you may need to continue treatment long term to maintain your full weight loss. In one trial, participants who stopped Wegovy regained about 70 percent of the weight they had lost within 48 weeks (UCSF News).

It is more honest, and often more motivating, to think of these medications as tools that make lifestyle changes more doable, not magic solutions that work on their own.

Get familiar with common side effects and risks

Every weight loss medication comes with the possibility of side effects. Some are mild and manageable. Others can be serious and require you and your care team to monitor closely.

Across prescription drugs, common mild side effects include:

Nausea
Constipation
Diarrhea

These are well documented by the Mayo Clinic and typically improve over time or with dose adjustments (Mayo Clinic).

The details depend on the specific drug:

GLP 1 agonists like semaglutide often cause digestive symptoms. In one analysis, about 44 percent of users reported nausea, 30 percent diarrhea, 24 percent vomiting, and 24 percent constipation, with smaller numbers reporting stomach pain, bloating, heartburn, or gas (Obesity Medicine Association). Some studies have linked these drugs with increased risks of pancreatitis, bowel obstruction, and gastroparesis compared to bupropion naltrexone (Obesity Medicine Association).
Tirzepatide, the active ingredient in Zepbound, can cause constipation, upset stomach, bloating, and diarrhea. More serious potential side effects include stomach, kidney, and gallbladder problems, pancreatitis, low blood sugar, and a warning about possible thyroid tumors or cancer (Obesity Medicine Association).
Bupropion naltrexone can raise blood pressure and carries a suicide risk warning that is similar to other antidepressant medications. Common side effects include nausea, headache, and constipation (Cleveland Clinic).
Orlistat, which blocks fat absorption, often triggers gas and diarrhea, especially if you eat a high fat meal while taking it (Cleveland Clinic).
Phentermine has stimulant like effects and can cause headache, overstimulation, high blood pressure, insomnia, rapid or irregular heart rate, and tremor. It is not appropriate for you if you have hyperthyroidism, glaucoma, heart disease, or a history of stroke (Obesity Medicine Association).

Because these drugs can raise heart rate or blood pressure, affect digestion so strongly, or have unknown long term impacts, you should only take them under close supervision from a healthcare provider with regular check ins (Cleveland Clinic).

A 2023 analysis also found that about 68 percent of people stop semaglutide or liraglutide within a year, with around 4.5 percent stopping due to side effects such as nausea, vomiting, and stomach upset (Obesity Medicine Association). That drop off is an important reality to keep in mind as you consider starting.

If you ever notice chest pain, trouble breathing, severe stomach pain, signs of pancreatitis, very low blood sugar symptoms, or mood changes, you should contact your provider right away or seek emergency care.

Consider the cost and access issues

Even if a medication looks like a good fit on paper, you will need to think through how you will actually obtain and afford it.

Some key points to consider:

Drugs like Wegovy, Ozempic, and Mounjaro (or Zepbound) can cost around 1,000 dollars per month if you are paying out of pocket, and insurance often only covers them for their FDA approved indications such as diabetes or obesity, not for general weight loss (UCSF News).
Newer GLP 1 medications like Wegovy have an estimated annual net price of about 13,600 dollars, while older drugs like phentermine can cost as little as 10 dollars (Obesity Medicine Association). That is a huge range, so you will want to talk through specific options with your provider and your insurance.
Some brands have experienced ongoing supply shortages, especially Wegovy, which has made it hard for people to find both starting and maintenance doses. In some cases, people have had to travel long distances to locate a pharmacy with stock (UCSF News).

If you are in the United States and your provider prescribes a medication, discount programs can sometimes help. For example, GoodRx lists discounted prices for medications such as Wegovy tablets, Contrave, Qsymia, and generic phentermine through coupons, with some prices much lower than typical cash costs (GoodRx).

Before you start, ask yourself honestly whether you can afford the medication long term and what you will do if there are supply issues that interrupt your treatment.

Plan the conversation with your healthcare provider

If you are still interested in weight loss pills after learning about the benefits and tradeoffs, your next step is a detailed conversation with a qualified provider.

Some questions you might bring to your appointment include:

Based on my weight, health history, and medications, am I a candidate for any prescription weight loss drugs?
Which medication would you recommend for me and why that one instead of the others?
How much weight might I realistically lose and over what timeframe?
What side effects should I watch for in the first few weeks and how will we manage them if they occur?
How often will you check my labs, blood pressure, or other health markers while I am on this medication?
Will I likely need to stay on this medicine long term to maintain my weight loss? What happens if I stop?
What will my total costs look like with and without insurance, and are there more affordable alternatives if coverage is limited?

You may also want to discuss non medication options such as structured nutrition programs, behavioral counseling, or bariatric surgery, depending on your situation. For some people, a combination of approaches works best.

Bringing it all together

Weight loss pills can be helpful tools, especially if you have obesity or overweight with other health problems and have not had enough success with lifestyle changes alone. On average, they help you lose more weight and improve health markers like blood pressure and blood sugar compared with diet and exercise alone.

At the same time, they come with real risks, digestive and cardiovascular side effects, long term safety questions, high costs, and the likelihood that you will regain at least some weight if and when you stop. They also require you to stay engaged with everyday habits like how you eat, how often you move, and how you manage stress.

If you are curious about whether weight loss pills are right for you, use what you have learned here as a starting point. Then take your questions to your healthcare provider so you can make a decision that fits your body, your budget, and your long term health goals.