Phentermine And Alcohol: What Happens When You Mix The Two?

by Dr. Ahmed Zayed
Published on May 13, 2024
image of a beer flow

Obesity has become a huge problem all over the world. Imagine this: since 1975, the number of people living with obesity has **skyrocketed by 300%**! According to the World Health Organization, back in 2016, about 1.9 billion adults worldwide were carrying a bit more weight than what’s good for them. And guess what? A massive 650 million of them are dealing with obesity or serious obesity, based on their Body Mass Index (BMI) (1). You really shouldn’t skip the chance to dig in more. You’re about to find some mind-blowing facts and tricks that not a lot of folks are aware of!

Even though obesity is so widespread today, it is vital to understand that this is a preventable condition – and when obesity has developed, it can be treated successfully.

Many diets, programs, and even supplements have hit the market over the last decade to help reduce the current trend of obesity among the worldwide population. The only problem is, many companies out there are trying to profit from the industry, instead of truly caring for those who have become obese.

For many people, turning to their doctors for assistance with treating their obesity is an ideal solution. Pharmaceutical drugs have been developed to assist in reducing weight among the obese, especially when obesity has caused a particular person to develop health-related concerns, whether psychological or physiological.

Phentermine is currently considered the most popular option for patients who are looking to turn toward a pharmaceutical solution to assist in the treatment of their weight-related issues. The drug is widely used today and often recommended to patients with obesity that affects their health. Doctors are usually required to prescribe the drug to patients, as Phentermine is considered a prescription drug in many countries.

Since alcohol usage is relatively high among the general population, including those who are obese, a common concern is the effects of mixing Phentermine and alcohol. In this post, we’ll consider the effects and usefulness of phentermine, take a look at the side-effects that the drug may produce alone, and also discuss the possible effects that could be experienced when having alcohol while taking Phentermine tablets.

What Is Phentermine And How Does It Work?

Phentermine is a pharmaceutical drug that is most commonly utilized to help patients who are obese lose weight. Phentermine is classified as an anti-obesity drug and primarily acts as a central nervous stimulant. What this means is that the drug works by reducing the patient’s appetite – and a large appetite is often what causes people to gain weight and eventually develop obesity.

In medical terms, Phentermine is a drug classified as a Sympathomimetic Amine Anorectic (2). In addition to suppressing appetite, the drug also works by increasing the Sympathetic activity within the patient’s body.

When a patient utilizes Phentermine, the drug will stimulate the release of three specific hormones in their body, including epinephrine, adrenaline, and norepinephrine. This is what ultimately causes the patient to feel less hungry; thus reducing their risk of overeating during any of their meals throughout the day, and reducing their hunger sensations between meals.

These effects also give the patient better control over their urges and can help them avoid binging on unhealthy foods in the middle of the day.
Multiple studies have been conducted on the efficiency of Phentermine, as well as the long-term effects that the drug may have on the human body.

In one case study (3), a female patient, 34 years of age, was administered an initial dose of 15mg Phentermine on a daily basis. The patient’s daily dose was gradually increased until she reached 37.5mg per day.

Prior to the administration of Phentermine to the patient in order to treat her obesity, the patient weighed 176 kg and had a BMI of 62.6. After one and a half year on Phentermine medication, the patient’s weight reduced to 153 kg and her BMI was 54.4. The doctors involved in providing care for the patients also noted an improvement in her glycemic control.

A scientific study (4) tested the effects of Phentermine on a group of healthy individuals, all with a BMI that was higher than 25. The participants were divided into two groups – one group received a daily dose of 37.5mg Phentermine, while the other group was provided with a placebo drug.

After the study concluded, scientists involved in the clinical trial found that patients who took Phentermine had much more significant results in terms of weight loss compared to the placebo group. The Phentermine group had an average weight loss of 6.7kg, as well as an average reduction in their waist circumference of 6.2cm. Mild side-effects were noted among some of the participants who were asked to take a Phentermine tablet daily, but no serious adverse reactions were reported in the study.

More studies are available that have been able to prove the fact that Phentermine administered daily to patients who are obese may yield highly effective results, especially when compared to placebo groups and alternative weight loss pills that are currently available on the market.

What Are The Side-Effects Of Phentermine Tablets?

Even though Phentermine is generally considered an effective drug to assist in treating obesity among the general population, it is important that patients are aware of the possible side-effects that they might experience while they are taking the drug. While most studies have reported only mild side-effects, there have been reports of more serious side-effects that patients definitely need to be wary of.

One scientific paper (5) explains that Phentermine has been withdrawn from Germany and is often seized in various countries due to the potential dangers that have been associated with the use of this drug. Numerous side-effects may develop when a patient opts to utilize Phentermine to help them lose weight and overcome their obesity.

The paper describes that one of the most important risks lies in the patient’s cardiovascular health. Phentermine has been shown to cause hypertension, a term used to describe high blood pressure. When blood pressure levels rise too high, it may lead to a number of unpleasant effects on the body, including damage to the blood vessels and arteries.

In addition to hypertension, patients are also at risk of vasculopathy and vasoconstriction when they use Phentermine. These effects seem to become even more serious with long-term use of Phentermine drugs.

Psychological factors have also been linked to the drug. Patients who start to rely on Phentermine to assist in controlling their weight may develop mental illnesses. There is also the concern about the patient becoming dependent on the drug, which may cause the patient to experience a number of unpleasant withdrawal symptoms when they decide to stop using the drug – or when their physician decides that the patient should not continue with Phentermine as a means of treating their obesity anymore.

There are other side-effects (6) that have also been linked to the use of Phentermine. In particular, patients may also experience the following adverse reactions to the drug:

    • The patient may develop insomnia, which can become problematic in their sleeping habits. Poor sleep then exposes them to further risks that can harm their mental and physical well-being.
    • Nausea and vomiting are often seen among patients who take Phentermine
    • Gastrointestinal side-effects may occur, which may cause the patient to experience an upset stomach, along with diarrhea. Constipation is also possible with the use of the drug.
    • Dry mouth is another relatively common side-effect of Phentermine.
    • Some patients may develop problems with their sexual performance. Low libido is often noted among patients who take the drug. Men may also be at risk of developing erectile dysfunction symptoms.
    • Heart palpitations, restlessness, headaches, tremors, hives, and hyperactivity are also adverse events that may occur while a patient is using the Phentermine drug to treat their obesity.

Combining Phentermine And Alcohol – What You Should Know

A relatively large number of pharmaceutical drugs are known to interact with alcohol – and Phentermine is no different. This drug is known to cause a number of potential side-effects and problems when a patient mixes it with the use of alcohol.

Doctors who prescribe Phentermine to patients often advise them to avoid the use of alcohol during the period in which they will take the drug, in order to prevent possible harmful effects that may cause the patient both physical and psychological harm.

Still, alcohol usage remains high, and many people who are obese enjoys an alcoholic beverage now-and-then. This is why it is crucial for these patients to understand what the combination of Phentermine and alcohol can do to them – knowledge of these potential interactions will help the patient better understand why it may be a better option to avoid alcohol for the time being and to first focus on becoming healthier and reducing their body weight.

Alcohol by itself can already cause a person to experience various side-effects – and the substance is addictive on its own. When Phentermine and alcohol are used together, the main concern is that alcohol may cause the side-effects of Phentermine to become more severe than they already are.

In patients who have not developed any side-effects from the use of Phentermine, adding alcohol to the mixture may cause an increase in their risk of experiencing these side-effects.

Since alcohol is known to irritate the stomach, gastrointestinal side-effects are very common amongst those individuals who decide to have an alcoholic drink while they are taking Phentermine. This may cause them to experience nausea, and they may start to vomit. They may also experience signs of xerostomia. Stomach aches and heartburn are also two relatively common side-effects that may develop.

It is also important to note that the risk of experience side-effects related to the cardiovascular system is higher when using both Phentermine and alcohol at the same time. The patient’s heart rate may be elevated even further than using any of these two alone, and they may experience abnormal increases in their blood pressure levels. Chest pains may also be experienced.

When it comes to using Phentermine, it is best for a patient to make the decision to stop using alcohol for a short period for time – at least until they have completed their course of Phentermine. This will help to minimize their risks and could potentially avoid a more serious issue from occurring.

Patients who are taking Phentermine and would like to have an alcoholic beverage should not simply stop using the drug. Cessation of the drug may cause withdrawal symptoms to appear. It is always advised to discuss this process with the doctor and to stop using the drug by first lowering the dose gradually.


While natural supplements and diet programs have been developed to address the worldwide obesity epidemic, pharmaceutical interventions have been proven to deliver more reliable results in terms of reducing body weight. Side-effects, however, are often experienced by patients who opt for Phentermine tablets.

When Phentermine and alcohol are combined, the likeliness of experiencing these side-effects are significantly increased, and existing side-effects may also be aggravated. Patients are advised to be cautious about using alcohol while they are undergoing treatment for their obesity with Phentermine tablets.