Complete Guide to Prescription and Over the Counter Diet Pills

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Are you thinking about using an over-the-counter weight loss pill? Or perhaps you heard about an FDA-approved diet pill that requires a prescription. Trying to find a safe medication to help you lose weight can be challenging. Use this guide to sort through the facts to find the best product for you.

How to Buy Weight Loss Pills 

There are two different types of diet pills that you can buy. They are prescription weight loss pills and over-the counter (OTC) weight loss pills, the latter of which also includes herbal supplements.

Prescription weight loss pills are medications that you get through your doctor. OTC diet pills and herbal weight loss supplements can be purchased without a prescription and are available in many vitamin shops and drugstores.

Generally speaking, weight loss pills have one of three goals:

  • To reduce your appetite, making it easier to make healthy food choices
  • To increase your body's ability to burn fat, creating a larger calorie deficit
  • To inhibit your body's ability to absorb the fat in the foods you eat

Talk to your doctor about current research regarding the products you're interested in. They will also be able to discuss how taking a diet pill might interact with your other medications and provide the best advice regarding the safety of new products.

The best resource for information regarding the use of any supplement or weight loss pill is your healthcare provider.

FDA Approval vs. Non-FDA Approval

Some diet pills are approved by the U.S. Food and Drug Administration (FDA). Others don't require FDA approval. This chart outlines what it means to have FDA approval as well as what it means if a diet pill is not approved by the FDA.

FDA-Approved Drugs
  • Drug is proven to be safe

  • Drug is proven to be effective

  • Drugs meet federal quality standards

  • Product benefits outweigh the risks

Non-FDA-Approved Pills
  • Safety not reviewed or approved

  • Effectiveness not reviewed or approved

  • Claims of what the product can do are not approved or verified

It is also important to realize that some diet pills contain ingredients not listed on their labels which are also not approved by the FDA.

A 2018 study looked at 317 different weight loss products and found that 269 of them (84.9%) contained sibutramine—an ingredient that was removed by the FDA in 2010—as a hidden ingredient. Though this substance helped reduce appetite short term, it has also been connected with mood changes, increased blood pressure and heart rate, and even amnesia.

Other hidden ingredients found in some of the weight loss pills were:

  • Phenolphthalein, a laxative that was removed by the FDA in 1999
  • Fluoxetine, a prescription antidepressant also known as Prozac
  • Ephedra, a substance banned in dietary supplements since 2004

The availability of diet pills via the internet has made these substances even harder to regulate and control. It also makes it more difficult to determine whether the product you buy has safe dosage levels, potentially increasing your risk of taking a toxic amount.

Herbal supplements are not considered medications and therefore do not have to follow the strict guidelines for safety that govern medicines.

Things to Consider

There are a few factors to think about before deciding to buy and use diet pills. These include:

  • Your medical history as taking weight loss pills could be dangerous for people with some conditions, such as those with heart disease, liver disease, hyperthyroidism, or glaucoma
  • Whether they may interact with your other medications, either intensifying or reducing your other medications' effects
  • If you allergic to any substances that could potentially be included in the weight loss pill
  • If you are pregnant or breastfeeding and, therefore, could potentially pass the ingredients on to your newborn or unborn child

Prescription Diet Pills 

The U.S. Food and Drug Administration (FDA) has approved a range of medications designed to help with weight loss. These use different mechanisms and may only be appropriate for certain people.


This prescription medication was approved by the FDA in 1999. Xenical (orlistat) is a lipase inhibitor, which means it works by decreasing the absorption of fat. People taking this medicine should follow a low-fat diet or they will experience uncomfortable gastrointestinal side effects from undigested fat in stools.


How the two drugs in Qsymia (phentermine and topiramate) work together to promote weight loss is not entirely known. Research suggests that the drugs suppress appetite and improve insulin sensitivity. 

Your physician may prescribe Qsymia if you have a body mass index (BMI) over 30 or a BMI of 27 and higher along with a weight-related condition such as type 2 diabetes or high blood pressure. The medication needs to be taken along with lifestyle modifications for sustained weight management.


Saxenda is an injectable medication that helps users reduce their food intake so they lose weight. Saxenda can be used by patients who are obese (with a BMI of 30 or more) or by patients who have a BMI of 27 or more and a weight-related medical condition such as type 2 diabetes, high cholesterol, or high blood pressure.


Contrave (naltrexone hydrochloride and bupropion hydrochloride) affects the central nervous system to increase the number of calories you burn and reduce your appetite. The pill is prescribed along with a reduced-calorie diet and exercise program to help people lose weight.


Vyvanse (lisdexamfetamine dimesylate) is FDA-approved for the treatment of a binge-eating disorder, but it is not approved for weight loss.


Phentermine is marketed under a long list of names, including Suprenza, Adipex-P, and Lomaira. It is prescribed only for short periods and works by decreasing appetite. The drug can be habit-forming. Side effects can include insomnia, constipation, and dry mouth.

Over-the-Counter Diet Pills and Supplements

If you don't have a prescription for a diet medication, you might consider an over-the-counter weight loss pill or supplement. While OTC medications are FDA-approved for safety and effectiveness, weight loss supplements are not. It's the responsibility of the manufacturers and distributors of herbal supplements to ensure they are safe.

So when you buy a diet supplement or a popular herbal supplement for weight loss you need to be very careful about what you buy. The FDA also does not approve most of the claims that companies make about their products. In many cases, weight loss claims are carefully crafted to make the product sound more effective than it is.


The only over-the-counter weight loss pill approved by the FDA is Alli (orlistat). It contains a lower dose of the same medication that is in Xenical. People who take Alli must limit fat intake and make lifestyle changes or they will experience uncomfortable side effects.

The product was voluntarily removed from the market in 2014 after a tampering scare, but the company re-released it with a tamper-evident package in 2015.

Garcinia Cambogia

Garcinia cambogia is derived from a fruit that grows in warmer climates. It is widely available at health food stores and from online vendors, but many of the claims made by sellers have not been supported by scientific research. There is little evidence to support its effectiveness.


The name of this diet supplement may not sound familiar, but you've probably seen products that contain the dietary fiber supplement. Lipozene for weight loss is one product that contains glucomannan. However, research has been inconclusive.

In 2020, the authors of a review study reported that they were not able to confirm that the fiber substance can actually promote weight loss.

Conjugated Linoleic Acid (CLA)

Conjugated linoleic acid (CLA) has been studied extensively, but weight loss results have been mixed. Check with your doctor before investing. One study published in 2016 found that some people who took this supplement experienced increased insulin resistance and lower levels of HDL cholesterol.

Raspberry Ketones

This weight loss supplement became popular after Dr. Oz mentioned it on his TV show. But there is just not enough evidence to support the claims that raspberry ketones can help humans lose weight.


Forskolin is an extract from the coleus forskohlii plant. It is advertised as a diet supplement, carb blocker, and fat burner. But there is very little evidence to support its use as a weight-loss supplement.


Meratrim is a mixture of extracts taken from the flower heads of the Sphaeranthus indicus plant and the fruit rind from Garcinia mangostana. A study of 60 participants with a mean BMI of 28.3 found that those taking Meratrim had greater reductions in their weight as well as in the size of their waist and hips.


Sometimes referred to as chromium picolinate, products that contain this substance often claim to help improve calorie burn and decrease appetite. However, while some research has shown a small correlation between chromium and weight loss, there is not enough evidence to support a more substantial claim. While chromium is generally considered to be safe, it is unlikely to promote weight loss.

Green Tea

Green tea can be consumed as a beverage or in pill form. It is often used to aid in weight loss, for improving mental alertness, or to lower blood pressure. While green tea is safe when consumed in moderation, there is little evidence to support its use as a long-term weight loss supplement.

Green Coffee Bean Extract

Green coffee is another name for raw coffee beans. A study of 64 obese women found that while they all lost weight on a low-calorie diet, those who received 400 mg of green coffee bean extract for eight weeks lost more weight than those who did not take the extract. They also had lower total cholesterol and LDL, or "bad" cholesterol, levels.


This herb is sold as an appetite suppressant. Hoodia is extracted from a flowering cactus plant (hoodia gordonii) and can be consumed in tablet, pill, or powder form. A 2019 review reports there is not enough scientific evidence to support the claims that hoodia is an effective form of long-term weight management. Moreover, its safety has not been adequately tested.

Bee Pollen

Though bee pollen has a number of health benefits, including antioxidant and anti-inflammatory properties, there is little evidence to support its use for weight loss.

In 2014, the company Oasis Bee Pollen was flagged by the FDA for making false and misleading claims about its product's weight loss effects. The FDA also warned of hidden ingredients in the company's supplement, including sibutramine, which can increase blood pressure, and phenolphthalein, which can cause cancer.

Banned Weight Loss Drugs

There are a few drugs that the FDA has banned for consumer use.


After Ephedra was banned in 2004, a number of similar stimulants took its place. Most advertise that they are ephedra-free and safe. They often contain bitter orange (citrus aurantium), synephrine, or octopamine. Two of the most popular products, Xenadrine EFX and Advantra Z, were tested by researchers in 2005 and still found to have unsafe effects on heart rate and blood pressure.


Meridia (sibutramine), an appetite suppressant, was removed from the market in the United States in 2010. The FDA initially approved the product, but the manufacturer stopped producing it after clinical studies showed that users had an increased risk of heart attack and stroke.


This drug was part of the anti-obesity medication Fen-Phen and worked by reducing carbohydrate cravings. However, the FDA withdrew its approval in 1997 after receiving numerous reports that women who had been taking this drug had developed valvular heart disease.


This appetite supressing drug—also known as Redux— was approved for a short period of time in the 90s, but the FDA ultimately withdrew its approval as well after concerns about its effects on the cardiovascular system. Like with fenfluramine, it appeared to cause valvular heart defects.


Belviq (lorcaserin) worked by activating serotonin receptors that regulate hunger. It was available with a prescription to patients with a BMI of 30 or a body mass index of 27 along with an obesity-related condition. In 2020, however, the FDA recalled Belviq from the market, citing cancer risks.

Since these banned drugs were once approved by the FDA, it serves as a reminder that even with FDA approval, there can be unknown risks of taking weight loss drugs.

A Word From Verywell

If the over the counter diet pills or weight loss supplements you're interested in are not listed above, visit the National Institutes of Health Office of Dietary Supplements. The NIH provides a comprehensive list of diet supplements along with current information about the safety and effectiveness of each one.

Always talk to your doctor about any diet pill or weight loss supplement that you are considering.

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Article Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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