Not everyone.

Prescription medication can help optimise weight loss progress for those who are above a certain weight or obese.

However, it is not a suitable option for those who:

  • have a BMI of 27 or less
  • are under the age of 18
  • have certain medical conditions
  • or are taking certain medicines.

What treatments are there?

In the UK Orlistat and Xenical are the only two licensed prescription treatments for weight loss (read our page on illegal diet pills for more information on what is and is not available). Alli is a similar medication which contains the same active ingredient, but is smaller amounts. 

In simple terms the above tablets work by binding fat in order to prevent it from being digested. Xenical and Orlistat cause one third of total fat consumed to be passed through the system as faeces, instead of being taken up into the bloodstream; and Alli one quarter.

Who can use them?

Not everyone looking to lose weight can use weight loss medication. There are specific criteria that must be met before it can be prescribed.

The body mass index scale or BMI is used as an indicator to identify those suitable for weight loss medication. It is calculated using weight and height.

A patient may be considered for weight loss medication if they have a:

  • BMI of 30 or above
  • or a BMI of 27 or above, and have another obesity related medical condition such as high blood pressure, high cholesterol or diabetes.

Weight loss medication will only be prescribed to patients who are dedicated to losing weight. Your doctor may ask about your plans to adopt a healthier diet and increase your physical activity, or help you to implement some.

Within the first three months of taking weight loss medication the desired amount of weight loss will be around five percent of your total weight. Your doctor may decide to stop the treatment and instead suggest alternative weight loss methods.

Who shouldn’t use weight loss medication?

  • If your calculated BMI is 25 or under then you should not use weight loss medication. It is not meant for those who are not classed as overweight or obese.
  • Weight loss medication is not recommended for use by pregnant women.
  • Women who are breastfeeding should not take Orlistat or Xenical, as it is unknown whether the drugs pass into breast milk.
  • Women who are concerned about weight gain during or after pregnancy should speak to their doctor.
  • Orlistat and Xenical are not licensed for use by those under the age of 18.
  • People with chronic malabsorption syndrome and cholestasis should not use weight loss medication. Those with chronic kidney disease should be carefully monitored when using this type of treatment.
  • Anyone allergic to any of the ingredients used in Orlistat or Xenical should avoid their use.

Other medications and weight loss treatment

Weight loss medication can interact with or alter the effectiveness of some other medicines. Your doctor will need to know of any other drugs or remedies you are currently using or have recently used.

This type of medication can cause some people to experience diarrhoea. This side effect can potentially impede the efficacy of the oral contraceptive pill. In these circumstances the user should look to adopt alternative contraception methods.

Lose weight safely

The reasons that drive a decision to lose weight can differ greatly depending on the individual. One person may be motivated by health related reasons whereas others might have personal fitness goals.

It is important to find a weight loss method that is sustainable and suits you. Weight loss medication can only be effective when used correctly and in tandem with a programme of healthy diet and exercise.

Page last reviewed:  20/04/2018