Mixing Phentermine and Alcohol: Risks and Side Effects

Last Medical Review: October 28, 2026
Posted On: Feb 6, 2023
Updated On: October 28, 2026
Amanda Stevens
Written by:

Amanda Stevens, B.S.

Dr. Erika S
Medical Review by:

Dr. Erika Steinbrenner, MD

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    What you will learn
    • Phentermine is a prescription medication that is commonly prescribed for weight loss.
    • Because of phentermine’s stimulant effects it can be misused and abused.
    • Alcohol can cause many different problems for those that take phentermine.
    • The effects of phentermine and alcohol can be severe.
    • Knowing the signs of phentermine and alcohol misuse can help someone seek the help they need.
    • Combining phentermine with other substances, including cannabis, may increase health risks.
    • Phentermine has not been convincingly linked to clinically apparent liver injury.

    Combining substances such as phentermine and alcohol can lead to a variety of undesired side effects, including the risk of becoming addicted to both substances. These side effects and risks can cause your body harm and cause the medication not to work as well as it should. Typically, when someone is prescribed phentermine, they are told they should not drink alcohol while actively taking the medication.

    What is Phentermine?

    Phentermine belongs to the class of sympathomimetic amine medications that are considered anorectics.[1] It is a prescribed drug that is used to help patients who are obese or have weight-related medical problems lose weight. It can also be used to help someone keep the weight off and prevent them from gaining it back quickly.

    Phentermine comes in extended-release capsules and tablets. Phentermine must be used with an exercise regimen and a healthy diet. This medication is commonly only prescribed for short-time use (less than 12 weeks).

    This drug may also be prescribed alongside topiramate when used for long-term weight loss. The combination of the two weight loss medications (called Qsymia) is commonly prescribed to people who have a body mass index (BMI) greater or equal to the 95th percentile.[2]

    There are many different brand names for the medication. These brand names include:

    • Adipex-P
    • Zantryl
    • Lonamin
    • T-Diet
    • Obenix
    • Phentercot

    How Does It Work?

    Phentermine works in the body as a stimulant. The medication will stimulate three specific hormones in the body which will help lead to appetite suppression. In the appetite centers of the brain, norepinephrine and epinephrine will be released.

    The release of these hormones into the body will help reduce the amount of food that is consumed at mealtimes, help someone avoid binging on unhealthy food, and reduce hunger between meals.

    This medication is chemically similar to amphetamine, another stimulant drug. Because it is classified as a Schedule IV controlled substance, it carries a risk of dependence and abuse.[3]

    Effects Of Phentermine

    Phentermine works in a different way than alcohol because it is a stimulant and not a depressant. While alcohol may make someone sleepy, phentermine will typically make someone more alert. The effects that phentermine has on the brain are different from alcohol.

    Some effects that phentermine has on the brain include:

    • Headache
    • Dizziness
    • Mood changes
    • Overstimulation
    • Psychosis
    • Insomnia
    • Restlessness
    • Tremors
    • Euphoria

    The Risks Of Combining Phentermine and Alcohol

    Because the two substances are very different in the way that they work in the body, if the two are combined it will cause various unpleasant side effects. This is why people who are prescribed phentermine are advised not to consume alcohol while taking the medication. Combining drugs and alcohol can also heighten the likelihood of developing a dependence on alcohol.

    Inhibits Weight Loss

    Even though phentermine is prescribed for weight loss, combining alcohol with the medication may cause someone to stop losing weight. Alcohol is full of calories and will cause someone to make poor decisions when it comes to food. This can cause the purpose of the medication to not be fulfilled.

    Cardiovascular Side Effects

    Supporting visual for Cardiovascular Side Effects

    Cardiovascular side effects may occur when someone mixes phentermine and alcohol. This is especially the case if they have a prior heart condition or disease prior to taking the medication.[4]

    Some cardiovascular side effects include:

    • Heart failure
    • Increased heart rate
    • Increased blood pressure
    • Chest pain

    Gastrointestinal Issues

    Alcohol can irritate the lining of the stomach, which will cause gastrointestinal problems if alcohol is combined with phentermine. Some of these problems include:

    • Nausea
    • Stomach aches
    • Vomiting
    • Heartburn

    Effects on The Central Nervous System

    Alcohol is a depressant that may cause certain problems to the central nervous system. It is important that if alcohol and phentermine are taken together, the person does not operate heavy machinery or drive a motor vehicle. Common effects on the CNS include:

    • Drowsiness
    • Difficulty concentrating
    • Dizziness
    • Depression

    Misuse And Abuse

    When phentermine and alcohol are used together, it may cause someone to become dependent on the effects of the drug combination. This is because phentermine is a stimulant, and alcohol can intensify that feeling. This is the greatest risk of mixing phentermine and alcohol. Misuse and abuse may lead to overdose, addiction, and even death.

    Phentermine And Alcohol Misuse

    Supporting visual for Phentermine And Alcohol Misuse

    Phentermine and alcohol are often combined to achieve a euphoric feeling. This medication is often misused by people who have a prescription for it, but it may also be found on the streets as well. While this medication doesn’t typically cause a psychological craving and dependence, it can still be abused for its stimulant effects.

    Signs Of Phentermine And Alcohol Abuse

    Signs of phentermine and alcohol abuse may be similar to those of other kinds of drug abuse. Those who drink alcohol heavily and take phentermine will likely have the same symptoms of other drug abuse.

    These signs may include:

    • Lying to be able to use or get more of the substances
    • Isolating from friends and family
    • Craving the substances
    • Getting the substances off the street or through other illicit means

    When someone is abusing phentermine, you might notice:

    • They smoke or snort the medication
    • Extreme weight loss
    • Someone who is not overweight begins using the drug (this can also be a sign of an eating disorder)
    • Having trouble concentrating without the medication

    Does Phentermine Affect the Liver?

    Phentermine has not been convincingly linked to liver damage. Available evidence has not shown a clear association between phentermine use and elevated liver enzymes or clinically apparent liver injury.[5]

    However, this does not mean that every person taking phentermine is free from liver-related risks. People with existing liver disease or concerns about liver function should discuss their medical history with their healthcare provider before starting the medication. Anyone who develops symptoms such as yellowing of the skin or eyes, dark urine, or persistent abdominal pain should seek medical advice.

    Other Phentermine Interactions to Watch For

    Phentermine can interact with certain medications and other substances, potentially increasing side effects or changing how medications work. Tell your healthcare provider about all medications, supplements, and recreational substances you use before taking phentermine.

    • Weed (cannabis): The interaction between phentermine and cannabis has not been well studied. Cannabis can affect heart rate, while phentermine can increase heart rate and blood pressure. Ask your healthcare provider about the potential risks of using both.
    • Other weight-loss medications: Combining phentermine with other weight-loss drugs is generally not recommended unless specifically directed by a healthcare provider, because the safety of these combinations has not been established.
    • MAO inhibitors: Phentermine must not be taken during or within 14 days of using monoamine oxidase inhibitors (MAOIs) because the combination can cause a dangerous rise in blood pressure.[6]
    • Certain antidepressants: The safety of combining phentermine with serotonergic medications, including some antidepressants, has not been established. Discuss these medications with your prescriber before taking phentermine.
    • Diabetes medications: Phentermine can change insulin or oral diabetes medication requirements, so doses may need to be adjusted by a healthcare provider.

    Treatment for Polysubstance Use

    Treatment for prescription stimulants such as phentermine may include a couple of different treatment methods. If someone is also suffering from alcohol use disorder, other approaches may be recommended.

    The first thing that will happen is the body will need to detox from the phentermine and alcohol. Withdrawal symptoms of alcohol can be dangerous and even life-threatening, so it is best done in a facility with medical staff. To detox safely from phentermine, the person using it may be able to taper off the drug. This can help with the overdose symptoms of the medication.

    Along with detox programs and advice, many people will be recommended to attend therapy. This can help treat someone who is addicted to stimulants such as phentermine and alcohol. Behavioral therapy can be done in a partial hospitalization or outpatient setting.

    Oftentimes, someone who is struggling with their weight will also have feelings of depression and low self-esteem. When an addiction is present along with other mental health issues, they will need to be addressed at the same time.

    Dealing with the challenges of phentermine and alcohol isn’t easy, but there’s always hope for recovery. At Epiphany Wellness, we’re committed to assisting you in reclaiming your life and embracing it fully.

    Frequently Asked Questions About Phentermine and Alcohol

    How long should you wait to drink alcohol while on phentermine?
    What other substances interact with phentermine?
    Can I smoke weed while taking phentermine?
    What are the overdose symptoms of phentermine?
    Does phentermine affect the liver?
    Sources

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