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Medicine information

Phentermine

An appetite suppressant chemically related to amphetamine. Phentermine holds no EU-wide authorisation for weight management.

General information, not medical advice. Docalo does not sell medicines, and prescription-only medicines are prescribed only after an individual medical assessment.

Talk to a doctor about weight care
Medicine information

What Phentermine is and how it works

Phentermine raises the level of noradrenaline in the brain, which reduces feelings of hunger.

In 1999 the EU's medicines committee concluded that phentermine and related appetite suppressants had not shown a favourable long-term benefit, and in 2000 the European Commission ordered their national authorisations to be withdrawn. The EU courts later annulled that decision on procedural grounds.

Authorisation status and label

  • In the United States, phentermine is labelled for short-term use, a few weeks, alongside diet and exercise, in adults with a BMI of 30 kg/m² or more, or 27 kg/m² or more with other risk factors.
  • It is a controlled substance in the US because of its potential for misuse.
  • It holds no EU-wide authorisation for weight management.

Only a doctor who knows your history can decide whether a medicine suits you.

How to use Phentermine

Short-term only. US labels describe use for a few weeks as part of a weight-reduction programme, usually once a day in the morning to avoid trouble sleeping.

Not combined with other appetite suppressants. US labels advise against combining it with other weight-loss medicines, because of reports of heart-valve disease and pulmonary hypertension with this class.

Common side effects

Get urgent medical help if (whatever the frequency): Breathlessness, chest pain, fainting or swollen ankles, A racing or irregular heartbeat, Swelling of the face, lips, tongue or throat, or trouble breathing

Reported with phentermine (frequency not set by an EU label): raised heart rate, palpitations, raised blood pressure, trouble sleeping, dry mouth, restlessness, constipation

Safety

Do not use Phentermine if

  • You have heart or blood-vessel disease, including uncontrolled high blood pressure
  • You have an overactive thyroid or glaucoma
  • You have a history of drug misuse, or are in an agitated state
  • You are pregnant or breastfeeding, or have taken an MAO inhibitor in the last 14 days

Breathlessness, chest pain or fainting can signal pulmonary hypertension or heart-valve disease, which have been reported with this class of appetite suppressants.

FAQs

Your questions answered

Phentermine3 questions
Is phentermine authorised in the EU?
Not EU-wide. The EU's medicines committee concluded in 1999 that phentermine and related appetite suppressants had not shown a favourable long-term benefit, and the Commission ordered withdrawal in 2000; the courts later annulled that decision on procedural grounds.
Its labels limit use to a few weeks because benefit beyond that has not been shown, while the risks of raised heart rate, raised blood pressure and misuse remain.
More questions
No. Qsymia combines a lower dose of phentermine with topiramate in one capsule and has its own label. Phentermine on its own is a separate, older medicine.

Other medicines used in weight management

Talk to a doctor about weight care

The Docalo membership gives you a doctor's assessment, a personalised plan and monthly follow-up. Your doctor decides what care suits you, with or without medicine.

Talk to a doctor about weight careGeneral information, not medical advice. Docalo does not sell medicines, and prescription-only medicines are prescribed only after an individual medical assessment.
All content on this page has been medically reviewed by: Dr. Alejandro Infante, General medicine, on 27 July 2026. Registration: 080869277

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