Are Weight Loss Pills Safe


Weight loss pills, or diet pills, are a type of medication that help to reduce or control body weight, usually through the suppression of appetite or by changing the way the body processes certain foods. They are usually prescribed by doctors when a person has made changes to their diet and exercise, but haven’t been able to lose weight. Weight loss pills also come in the form of supplements. Weight loss pills should be used alongside a healthy diet and physical activity, and shouldn’t be used instead of these. Similar to other types of medicines, certain weight loss pills will work better for some people rather than others, and the side effects will vary from person to person. There are also some small risks associated with certain weight loss pills. So are weight loss pills safe? 

Are weight loss pills safe?

There are various types of diet pills, some of which are more suitable to certain people than others, and only some of them are legal. Some weight loss pills, such as sibutramine, have been suspended from being sold in the past due to the risks associated with taking them. Sibutramine, which was also known as Reductil, was suspended by the Medicines and Healthcare products Regulatory Agency in 2010 as there were links between the weight loss pill and an increased risk of heart attacks and strokes. Additionally, rimonabant, also known as Acomplia, was suspended after it was found to be linked to an increase in the likelihood of worsening mental health issues and the development of psychiatric disorders.1

Orlistat is currently one of the most popular weight loss pills, as well as being recommended by the NHS and able to be prescribed by doctors and pharmacists. This pill works through the absorption of fat from the diet by reducing lipase - an enzyme which breaks down fats in foods. Orlistat has been found to be safe for usage although there are a small amount of risks. These risks are very uncommon, and include haemorrhaging, hepatitis, and inflammation of the pancreas - this is known as pancreatitis. 

Weight loss products also exist in the form of herbal medicines, which contain natural ingredients. Herbal weight loss supplements made from garcinia cambogia, a fruit which contains hydroxycitric acid,2 are appetite suppressants, and studies suggest that these dietary supplements have very little effectiveness for weight loss.3 The usage of products containing garcinia cambogia have been linked to some cases of liver damage, and although they were quite uncommon, some of the cases were severe.4 These cases occurred when the supplements contained other ingredients alongside garcinia cambogia and when the supplements contained only garcinia cambogia. 

Green tea extract pills, which are also herbal dietary supplements, have been found to aid in weight loss in high doses. This supplement works through increasing the number of calories that are burned by the body through producing more heat - known as thermogenesis.6 This form of weight loss pill is not considered to be safe, as high doses of green tea extract can be toxic and can cause damage to the liver. 

The usage of weight loss pills depends on the person taking them, and it is important to discuss the variety of options with a doctor to ensure that the option chosen is the best one. 

Who can take weight loss pills?

Generally, weight loss pills are recommended for people who have a BMI of 30 or higher or are struggling to lose weight through the traditional methods - maintaining a healthy diet and daily physical activity. In some cases, doctors will prescribe weight loss pills to people with a BMI of 28 if they have another health issue such as high blood pressure or type 2 diabetes.5 However, the suitability of certain weight loss pills depends on the person taking them - for example, Orlistat is not recommended for people who find it hard to keep a low fat diet. 

Weight loss pills are not recommended to be taken by women who are trying to get pregnant, women who are currently pregnant, and women who are breastfeeding. People who have kidney disease should discuss the use of orlistat with a doctor, as there is a very small chance that the use of this weight loss drug has the possibility of causing hyperoxaluria which in turn causes damage to the kidneys. 

Side effects of weight loss pills

As with most types of medication, weight loss pills can cause various side effects which differ from person to person. One weight loss pill, recommended by the NHS, is orlistat. This pill can cause side effects such as fatty or oily stools, as well as needing to go to the toilet more often, and oily discharge from the rectum. These side effects are caused by the reduction of absorption of fat due to the orlistat, and the best way to reduce the likelihood of these side effects is to maintain a low fat diet. Additionally, it is possible to experience diarrhoea whilst taking orlistat, and people taking the oral contraceptive pill at the same time will need to use additional contraception if they experience diarrhoea, as it may prevent the contraceptive pill from being properly absorbed, making it ineffective. Liraglutide, which is not a pill but a daily injection, can cause nausea and possibly vomiting. 

What pills are approved and safe for weight loss

Most weight loss pills that are available today, and that are prescribed by the NHS, have undergone clinical trials and have been found to be safe to be used. These trials have found that the best weight loss pill, which is also the only weight loss pill considered to be safe and effective by the NHS, is orlistat. Orlistat can only be used if a doctor or a pharmacist recommends it, and is generally only available through prescriptions. This weight loss pill works by reducing the amount of fat which is absorbed into the body when eaten, causing the unabsorbed fat to pass through the digestive system. This means that someone taking orlistat is more likely to avoid gaining weight, rather than lose weight. Liraglutide, a weight loss medication which is not a pill but is also recommended by the NHS, has been deemed to be safe and is often prescribed if orlistat doesn’t work. This medication is also used to help manage type 2 diabetes. 


There are a large variety of options when it comes to weight loss pills, some of which are medications and others which are herbal medicines and remedies. Each form of weight loss pill comes with its own possible side effects, as well as the possibility of risks, which manifest differently in different people. Weight loss pills that have been found to have larger risks than others have been removed from the market, and are unable to be prescribed to people. Weight loss pills that are still on the market have been found, through numerous clinical trials, to be safe with very little risks. Overall, weight loss pills that are available for prescription through doctors and pharmacists are safe to be used, but the options should be thoroughly discussed with a doctor to ensure that the best choice is made. It is important that those who are considering taking weight loss pills or who are currently taking weight loss pills should maintain a healthy diet and regular exercise alongside their prescription for effective weight loss. 


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  10. Mayo Clinic. Pros and cons of weight-loss drugs [Internet]. Mayo Clinic. 2018. Available from:
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Jade Howlett

Bachelor of Psychology – BSc Psychology, University of Hull, England

Jade is a student at the University of Hull in her final year of her undergraduate course, with particular studies in Health Psychology. She will be pursuing a master’s degree in Artificial Intelligence and Data Science with the interest of combining the disciplines of Psychology and Artificial Intelligence.

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