Along with the well-known physical phentermine side effects such as dry mouth and insomnia, this popular weight loss medication can also cause emotional side effects like low mood, anxiety and irritability.
In fact, increased anger, or dysphoria, due to phentermine is so common that it even has its own nickname: phen rage.
Phentermine Mood Swings
Mood swings are a common side effect of this medication, with nearly 40% of users experiencing phen rage, low mood or anxiety during treatment (
With more than 1 in 5 of patients reporting dysphoria at some point during treatment, phentermine anger issues are one of this medication’s most commonly-reported side effects (
More specifically, phen rage describes the feelings of frustration, impatience, hostility, irritability, and anger that patients feel while taking phentermine. In most cases, this anger is directed outwards in angry outbursts, shouting, and even physical destruction or violence.
If you or your loved ones have noticed that you are suddenly overreacting to situations or consistently in a bad mood since beginning phentermine, talk to your doctor.
How Long Does Phen Rage Last?
Like most phentermine side effects, Phen Rage is usually most severe at the beginning of treatment. Using the experiences of past and present Facebook support group members as a guide, phentermine anger and irritability can last anywhere from a few days to few weeks.
Can You Prevent Phen Rage?
There is no proven method to prevent phen rage, or any other phentermine side effect. Thankfully, this reaction does not occur in every patient.
If you are concerned about phentermine-related anger, the below lifestyle strategies may help minimize your risk of developing phentermine mood swings.
Why Does Phentermine Make Me Angry?
Phentermine acts as a stimulant to help you lose weight faster and easier, but intense emotional changes can emerge as an unwanted side effect along the way.
Here are two possible explanations for phentermine mood swings and phen rage:
The ‘Fight’ Response
Phentermine activates the limbic system and triggers the adrenal glands to release higher levels of catecholamines, known colloquially as the “fight or flight” hormones.
These chemicals are beneficial for weight loss because they suppress appetite and trigger the release of extra glucose into the bloodstream, which boosts energy and promote activity.
However, these hormonal changes also produce an undesirable emotional response in some phentermine users.
The body associates these chemicals – including adrenaline and norepinephrine – with stress. Even though the human body is an ornate & finely-tuned organism, it cannot biologically distinguish between real stress (from anger or fear) and stimulant-induced activation.
As a result, when phentermine kicks-in, the brain and body may start “helping” you get ready to fight even though there is no actual danger. In some people this can lead to phen rage, including irrational behavior and uncharacteristically extreme reactions.
But it’s not only anger. Many phentermine users report amplified reactions to both positive and negative situations while taking this medication: whether that’s feeling high when happy, depressed when low, or rageful when bothered. Like phen rage, this more general emotional polarity is likely related to hormonal changes.
Hormonal Fluctuations Related to Weight Loss
Quick, dramatic weight loss can also affect hormones.
Major weight loss affects hormone levels because of changes in metabolic rate, different eating and exercise habits and decreased body fat percentage.
Estrogen, for example, is produced in fat cells, so less adiposity often correlates lower levels of this sex hormone. Hormonal fluctuations can cause phentermine mood swings, in some way comparable to spells of irritability associated with PMS, pregnancy, perimenopause or menopause.
How to Cope with Phen Rage (Dysphoria)
Side effects fueled by biological reactions like hormonal changes are hard to control, so overcoming phen rage is not always easy. However, some simple strategies can help you feel less angry and more in-control while taking phentermine.
If you have noticed phentermine anger bubbling up occasionally, try the below tips for how to avoid phen rage:
1. Prioritize Sleep
Sleep deprivation leaves people tense, irritable and prone to anger (
2. Take a Timeout
Timeouts are usually reserved for kids, but they can help avoid angry outbursts too. When you feel yourself working up to a breaking point, walk away and take a quick break. A few moments of quiet might provide some necessary clarity to deal with the situation at-hand without getting angry.
3. Seek Support
Family, friends and colleagues are likely to bear the brunt of your phentermine anger.. If you’ve been losing your temper a lot, talk to loved ones about the medication and explain how the things you have said and done recently don’t always represent your true feelings.
4. Get Active
Breaking a sweat boosts endorphins, relieves stress and gives you a positive outlet for the extra energy from phentermine (
5. Avoid Alcohol
Avoid alcohol while taking phentermine due to the increased risk of adverse side effects like hypertension, dizziness and lightheadedness (
6. Identify Triggers
Although phen rage can strike as a result of seemingly trivial situations, identifying why these events cause angry outbursts may help to avoid future problems. If a specific person or situation is causing anger or resentment, find a calm moment to discuss your frustrations rather than let this frustration build up into an angry outburst.
7. Eat Nutritiously
Diet is an often-overlooked cause of phentermine irritability. To avoid “hangry” outbursts, plan frequent, nutritious meals and snacks filled with a wide range of nutrients.
Supplements and Herbs for Phen Rage
After a few days of rage irritability, frustration and impatience, some users consider supplements and herbs to manage phentermine mood swings. In most cases, natural remedies are not effective given the cause and severity of phentermine anger.
However, these herbs and supplements have purported benefits to control anger and bring calm (
- Members of “Losing Weight with Phentermine” Support Group on Facebook & Phentermine.com Forum. (2019, March 13). [User Report of Common Phentermine Side Effects]. Unpublished raw data.
- WebMD. (2019). Phentermine Oral: Uses, Side Effects, Interactions, Pictures, Warnings & Dosing.
- Johns Hopkins Medicine. (2018). The Effects of Sleep Deprivation.
- Mayo Clinic Staff. (2018, March 08). Exercise and stress: Get moving to manage stress.
- Drugs.com. (2019, January). Phentermine and Alcohol / Food Interactions.
- American Addiction Centers. (2019). Treating Anger Disorders – Anger Management Treatment Options.