5 Most Common Myths About Phentermine Debunked

by Marixie Ann Obsioma, MT, undergrad MD on November 28, 2018
Last updated on May 23, 2021

Phentermine has received some backlash over the past few years. There are so many displeasing claims about its effects on the body. As a result, a lot of people have lost interest in what it can offer.

phentermine myths - an illustration of a newspaper with the stamp 'FAKE NEWS'

Who would want to suffer grave consequences just to shed some extra pounds?

Not too many, right?

In all honesty, though, everything has its own pros and cons. So yes, there may be some drawbacks that come with taking phentermine to get rid of the excess pounds, but not everything about it is true.

But first, what is Phentermine and what are its positive effects on the body?

Phentermine is marketed as an appetite suppressant. It has the similar composition as amphetamine, a highly addictive component. The reason why phentermine entered the mainstream of dieting and exercise is that it is marketed as a perfect adjunct to exercise. It also lowers down the caloric intake of someone who wants to stay on the friendly side of the scales.

Here are some of the things often said about phentermine that is not worth your attention. Brush off these five pieces of false information when you hear it:

1. There are tons of claims that state they gained their former weight after ending the use of phentermine.

The rebound effect is something no one in the right mind will sign up for. Fortunately for people who want to try phentermine, this should not be a cause of concern. The thing is only you can determine if you are to retain your new weight and preserve the weight loss provided to you by phentermine. If you sustain a healthy lifestyle, there is a little to no chance that your previous weight will come back to haunt you (1).

Phentermine is meant to be taken in a short period of time. The negative effects will do your body more harm than good in the long run, so you should not expect to use it for prolonged periods. The best thing you can do is try to learn and adopt a healthier lifestyle while on the medication to ensure that once you get off it, you are off to a fresh start.

2. Taking birth control pills with phentermine is a major no-no.

Contrary to the above statement, it is a good idea to use contraceptives while on phentermine (1). Being a psychostimulant, the drug is never good for a pregnant woman, let alone an unborn child. You should never put yourself on this risk.

Although it does not come as a total shock for many women to worry about the potential interaction between the two drugs, phentermine does not have any effect on birth control pills. Unfortunately, though, it has been related to some breakthrough bleeding (1). The flow of blood is probably due to the body’s need to compensate due to the lack of estrogen. One medication can decrease the positive effects of birth control pills. This, in turn, can lead to spotting. In this case, it is always a good idea to use other forms like condoms.

No matter what is being prescribed, it’s important to talk to your physician about using phentermine and birth control. You need to disclose all your issues and concerns firsthand to ensure the safest approach for you.

3. You can take phentermine for as long as you like.

As mentioned earlier, phentermine is not meant as a lifelong solution. In reality, the only approved period of time for phentermine is three months (2). In some cases, using it for more that than that may wreak havoc to your system. Additionally, it is highly addictive. If you use it more than the prescribed period of time, it may lose its effects as you develop tolerance.

If the doctor thinks that you can get a lot from using the drug, the approach would be to put you in a couple of phentermine rounds. This is usually interrupted with a month-long rest from using the medication. Of course, this is pretty uncommon. The evaluation is based on your physician’s stand and understanding of your body’s needs.

4. You can skip the gym when on phentermine.

Active people can get a kick from working out to speed up the positive results. There are rumors spreading in forums and online support groups that you do not need exercise when on the drug. Unless your physician explicitly told you that you are in no state (probably stemming from other physical issues) to work out, then there is no reason why exercising should not be included in your weight loss to-do list.

If you are not that physically active, start slowly. So long as you are moving, you can help move things forward in your journey to removing the unnecessary weight. A half an hour a day can give you a lot of benefits compared to stating sedentary (1). Once you have decided to continue on your exercise routine, incorporate strength training and cardio.

5. Phentermine is for everyone’s disposal.

Using phentermine requires careful consideration. You cannot expect your physician to just hand it put to you just because you said you want to say bye to your belly fat. It is an ideal treatment for exogenous obesity and is considered a very potent medication. Generally, people with BMI of more than 20 or those who have it more than 27 coupled with a risk factor like high blood pressure or diabetes are found to be most suitable patients in using the medication (1).

Individuals who are blessed with normal weight (even those with a little-added pounds) or who have heart problems should never use phentermine. Also, certain medications can ruin phentermine’s ability to reduce weight without many risks. Always check with your physician or pharmacist on whether so and so the drug is safe to take with phentermine.

If you encountered a physician who is not giving you phentermine no matter how desperate you are to have it means that it is probably not safe for you. No matter how you desire to shed the extra weight from your body, you should always think of your overall health.

While these pieces of intel are running wild on the rumor mill, it is important to understand the risks involved in taking medications containing phentermine.

The usual gastrointestinal symptoms are expected, but in some rare cases, people have an increased chance of developing these two problems:

Primary Pulmonary Hypertension

As rare as it may be, this problem is pretty serious because it is fatal. PPH is like having a stroke and having the arteries in the lungs getting blocked. Not only that, it also causes a blockage on the right side of the heart. The usual signs are shortness of breath, palpitating heart, dizziness, cyanotic blue lips and skin, swelling of legs all the way to the ankle, and feeling fatigued all the time (3).

Valvular Heart Disease

Since the drug can heat up your valves, it might be difficult for it to close properly. If it does not close properly, it may leak and cause an interrupted flow of blood from the heart and extending outwards towards the rest of your body. Typically expected symptoms are weakness, shortness of breath even while at rest, edematous feet and ankles, chest pain, fatigue, and fast heartbeat (3).

While these two are rarely experienced upon usage of phentermine, the following symptoms are very much possible to contract:

  • Having a terrible taste inside the mouth
  • Feeling constipated or bloated
  • Having diarrhea and an upset stomach
  • Drying of the mouth
  • Vomiting
  • Pain in the head

These symptoms are bound to go away after a few weeks’ time. If it persists, then you might try and reach out to a physician. But before that, just wait it out.

Another way to ensure that you take phentermine properly is to not use medications that may interact with the effects of the medication. Some of the medications to hold off for a while are:

  1. MAO inhibitors
    Do not take phentermine within two weeks after the last dose of MAOI (4).
  2. Weight loss drugs
    Do not try to boost up your weight loss story by overloading your body with benzphetamine, diethylpropion, phendimetrazine and so on. Using these drugs with phentermine will drive you to a hypertensive crisis.
  3. SSRIs
    The drugs intended to treat depression can also double the negative effects of hypertension.

Aside from people with hypertension and cardiovascular concerns, those who have hyperthyroidism, glaucoma, and diabetes should always confirm with their physician if they can take the drug. Phentermine is known to stimulate thyroid activities. People with hyperthyroidism do not need more of that. In terms of eye pressure, glaucoma is already bad enough. Using phentermine can increase it and lead to a permanent loss of vision. Lastly, those with diabetes, it is safe to use phentermine but with special modifications on the dosage of the drugs used with diabetes (4).


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