Withdrawal Symptoms

Phentermine Withdrawal Symptoms

Most people use prescription weight loss pills for a few weeks at a time and do not experience any significant phentermine withdrawal symptoms at the end of treatment.

However, if phentermine is taken for long periods of time, at high doses, or abused, it can be habit-forming. The resultant mental and physical dependence increases users’ chance of experiencing phentermine withdrawal symptoms. Unfortunately, some users also report phentermine withdrawal symptoms after just short-term use.

Common Symptoms

Woman with holding head in hands
Some patients suffer from phentermine withdrawal symptoms after treatment ends

Withdrawal occurs when an individual stops taking a medication or recreational drug after developing a physiological or psychological dependence ( 1 ).

Withdrawal symptoms from appetite suppressants like phentermine may include:

  • Severe tiredness or weakness (fatigue)
  • Depression (or other mood changes)
  • Insomnia (trouble sleeping or nightmares)
  • Nausea or vomiting
  • Stomach cramps or pain
  • Trembling

Contact your doctor or seek medical attention right away if you experience any phentermine withdrawal symptom that is severe, worsening, or interfering with your daily life.


tired woman rubbing her eyes
Fatigue is one of the most common phentermine withdrawal symptoms

Phentermine stimulates the central nervous system, which gives users a noticeable boost of energy throughout treatment. After stopping phentermine, some people experience feelings of weariness and fatigue due to the sudden lack of chemical stimulation.

If you are tired after stopping phentermine, take care to:

  • Get enough sleep
  • Fuel your body with healthy foods: avoid high-fat, high-carb, and high-sugar goods that may worsen fatigue
  • Stay lightly active
  • Normal energy should return within a few days.

Contact your doctor if the fatigue is severe or doesn’t go away.


teenage girl sitting on the ground, looking depressed
Contact a doctor if you experience mood changes after stopping phentermine

Phentermine affects the natural levels of two neurotransmitters – norepinephrine and dopamine – that play a major role in mood regulation. After stopping phentermine, it can take a few days for the brain to readjust.

As a result, sadness and low mood are common phentermine withdrawal symptoms. For people with an underlying predisposition to anxiety, depression, or other mental illnesses, these symptoms can prove particularly worrisome and harmful.

Depression, with or without suicidal ideation, is a very serious stimulant withdrawal symptom. If you are experiencing depression, a medical professional needs to know so that he/she can help you.

On the other hand, if you’re just feeling a little down, a short workout, talking to a friend or taking a moment for self-care can help can help life your mood.

Contact your doctor or seek medical attention right away if you or a loved one is unusually depressed, hopeless, anxious, or down after stopping phentermine.


woman scrolling through her phone while laying awake in bed
Insomnia may get worse during withdrawal from phentermine

Trouble falling and staying asleep is linked to phentermine use: both as a side effect while taking the medication and as a withdrawal symptom after stopping.

Since phentermine stimulates the nervous system, most patients recognize the cause of insomnia during treatment. However, depression – a problematic phentermine withdrawal symptom – can also cause severe sleep problems.

Contact your doctor if insomnia lasts for more than a few days or interferes with your normal ability to function.

Nausea, Vomiting, or Stomach Pain

young woman covering her mouth during a wave of nausea
Nausea is a bothersome but manageable phentermine withdrawal symptom

Gastrointestinal symptoms like nausea, vomiting, and stomach pain are common reactions when someone withdraws from certain drugs or alcohol. They occur because of drug-induced changes in neurotransmitter levels.

Thankfully, GI upset is usually manageable at home and resolves within a few days. If you have nausea, vomiting, or stomach cramps after stopping phentermine, try OTC remedies like Pepto-Bismol or motion sickness bracelets (PSI bands).

If you have frequent vomiting or diarrhea, keep a close eye on hydration. When you feel able to eat, choose bland foods like bananas, rice, applesauce, and toast ( 4 ).

Contact your doctor or seek immediate medical attention if you can’t keep liquids down, see blood in your vomit or stool, or still have withdrawal symptoms a week or more after your last dose of phentermine.

How to Avoid Phentermine Withdrawal Symptoms

Scientific literature maintains that stopping phentermine does not cause withdrawal symptoms.

However, a significant number of patients still report symptoms. So, if you are concerned about withdrawal from phentermine, talk to your doctor. The two of you can discuss a plan for how to how to stop phentermine and minimize any potential withdrawal symptoms.

Always follow your doctor and pharmacist’s exact instructions.
NEVER adjust phentermine dose or schedule without consulting with a medical professional first.

Slowly Decrease Dosage

Gradually tapering down to a lower dose can prevent, or at least reduce, phentermine withdrawal symptoms.

If you have been taking phentermine in high doses or for a long period of time, it is especially important that you do NOT stop suddenly.

The wide variety of phentermine doses, ranging from 8mg to 37.5mg, makes it easier for patients to slowly decrease their dose. Higher-dose tablets can also be broken in half to reduce dosage.

Young woman sipping on water during a run around the park
Staying active and hydrated may help relieve some phentermine withdrawal symptoms

Prioritize Healthy Habits

Prioritizing healthy habits, especially as treatment comes to an end, may also help reduce phentermine withdrawal side effects.

Invest the time to learn healthy eating habits and incorporate more activity into your daily life. It’s also important to get enough sleep, take time to relax, and tend to your emotional needs. A strong self-care and healthy living routine will help you adjust to life without phentermine, both by minimizing withdrawal symptoms and by promoting weight maintenance.

Back to Phentermine Withdrawal page

  1. Center for Substance Abuse Treatment. (1999). Chapter 5 – Medical Aspects of Stimulant Use Disorders. In Treatment Improvement Protocol (TIP) (Ser. 33).
  2. Allina Health. (2013, June 12). Appetite suppressant, sympathomimetic.
  3. Drugs.com. (1999, April 26). Phentermine Hydrochloride Drug Information, Professional.
  4. Hartney, E., & Gans, S. (2018, November 12). 6 Tips For Coping With Withdrawal-Induced Nausea and Vomiting.