Using Phentermine During Pregnancy – Is It a Good Idea?

by Dr. Ahmed Zayed
Published on July 12, 2024
pregnant woman holding flowers

Managing your weight during pregnancy might seem as tough as scaling a peak. Lots of expectant moms grapple with the anticipated weight gain that accompanies carrying a little one. Therefore, a bunch of people are always searching for that perfect method to keep things balanced. Yet, what’s the golden ticket to getting it right?

Of course, the best idea is to consult the doctor on the topic. He/she can recommend a proper diet plan that will include all of the food groups and with that all of the vitamins, minerals, and nutrients in amounts that are required during pregnancy. Because once again, a good diet and a proper exercise plan are what your body needs in order to maintain a healthy weight. 

Perhaps you have heard about a little something called Phentermine. Maybe you have heard people talking about this quality weight loss drug, and you are wondering if and how you can use it to lose some weight during your pregnancy. 

But the question is – should you use Phentermine during your pregnancy? Is it totally safe for both you and your unborn child? And if you do proceed to use it, are there any potential side-effects that you should expect to occur? While all of these are good questions, they are questions that you should ask your doctor to answer. But we as well, have something for you too. 

In the following article, we will use our knowledge on the topic of Phentermine and explain to you everything that you may need to know about this surprisingly effective weight loss drug and the possibility of using Phentermine during your pregnancy. Follow us and get the answers to your questions that you have been looking for.

Phentermine – What is it and how does it work?

Phentermine is the name that is being used to refer to a prescription-only weight loss drug, or more precisely – the best weight loss drug available only with a doctor’s prescription in the United States that has been approved by the FDA. Yes, Phentermine really does wonders when used as recommended. It is a weight loss drug used in the treatment of obesity and overweight (1). Phentermine is a methamphetamine-like drug that stimulates certain parts in your brain in order to reduce your hunger and boost your energy levels. But why, you wonder? 

You see, Phentermine is meant to be used only in combination with a healthy diet and regular exercise, at least five times a week. Used in any other way would not produce the expected, beneficial effects. After all, Phentermine is not some kind of a magic pill that will deliver results without any additional effort. By reducing your hunger and boosting your energy, you will automatically feel better and able to follow your diet plan and have the energy to exercise five times a week. Unfortunately, Phentermine does come with certain potential side-effects that you would want to avoid. Let’s see which side-effects we have on mind, shall we?

The potential side-effects of Phentermine

Like any other drug, Phentermine as well is able to cause certain potential side-effects to occur. These side-effects mostly develop as a result of abuse or misuse of Phentermine, which is why it is essential to follow the instructions that your doctor has given you regarding your use of Phentermine. The Phentermine dosage is not something that you should interfere on your own. Your doctor is the only one who is able to do any changes in terms of increasing and decreasing the dosage. 

The reason why we are saying all of this is the fact that once the side-effects of Phentermine occur, they can quite easily cause discomfort in your life. The potential side-effects include dry mouth, gastrointestinal symptoms including diarrhea, constipation, nausea and vomiting, insomnia, high blood pressure, nervousness, irritability, and even addiction. Addiction is perhaps the most dangerous side-effect of them all (2). 

Since Phentermine is meant to be used for a short period of time only – around 12 weeks, anything above that or any interference with the dosage on your own can easily lead to addiction. As soon as you discontinue your use of Phentermine, you are exposed to the risk of experiencing withdrawal symptoms – including weight gain, irritability, insomnia, etc. In order to avoid the risk of experiencing any side-effects, we alert all of our readers to respect the prescribed dosage and follow the doctor’s instruction closely. 

Is it safe to use Phentermine during your pregnancy?

During your pregnancy, and before it for that matter, it is highly important to watch what you are introducing to your body. Your body requires all of the essential vitamins, minerals, nutrients, enough water, and only the best care possible in order to prepare itself for what is coming in the next nine months and offer your baby a warm home during those nine months. And that is how we are reaching the question of – should you take Phentermine during your pregnancy?

As we mentioned earlier, Phentermine is an FDA approved, and the doctor prescribed weight loss drug. This means that your doctor is the one that is able to make the decision on whether or not you are supposed to take Phentermine during your pregnancy. We are here only to help you understand that decision better and answer any questions that you might have (3).  

As a general rule, doctors avoid prescribing Phentermine to pregnant or breastfeeding women. The chances are that is what your doctor is doing in your case – refusing to prescribe you Phentermine to help you control your weight better. But why is that? 

According to the FDA, Phentermine belongs to a group of drugs called pregnancy category X. The drugs of the pregnancy category X, are drugs that have been studied in pregnant women or pregnant animal subjects. The results of these studies have demonstrated fetal abnormalities. In the case of pregnancy category X drugs like Phentermine, the risks of Phentermine being used during pregnancy outweigh the potential benefits. That is why it is highly unlikely that any doctor will ever prescribe Phentermine to a pregnant or a breastfeeding woman.  

In this case, we are unaware of the potential side-effects of Phentermine in the case of pregnant women, which is why, in most cases, Phentermine is not prescribed to pregnant women. On top of that, we mentioned earlier of Phentermine being a methamphetamine-like drug. Well, methamphetamine drugs’ effects during pregnancy have been investigated. And guess what? The results are not satisfying. 

The use of methamphetamines during pregnancy has resulted in an increased number of miscarriages and birth defects (4). This is a rather strong reason to avoid taking any methamphetamines during pregnancy if you ask us. Taking a combination of Phentermine and Fenfluramine, another popular weight loss drug, during pregnancy has actually caused a rare birth defect known as pulmonary hypertension. That is why this combination is no longer available to be used. We strongly advise you to avoid taking anything like in the interest of your baby’s health.

In conclusion, since Phentermine’s effects have not been investigated enough during pregnancy, and since Phentermine is not necessary to be taken during pregnancy, we advise our readers to avoid taking it during the following nine months and consult their doctors about it. You would not want to harm your awaiting child just because you want to lose weight in a more convenient way, do you? 

Instead, we advise you to try the following ways to maintain a healthy body and mind as well as a healthy body weight during your pregnancy, without the help of Phentermine. And who knows, perhaps when you are past your pregnancy, and your breastfeeding period, you can revisit the idea of using Phentermine to achieve a healthy body weight!

Maintain a good body weight during pregnancy with these tricks!

  • Improve your diet – Ask your doctor to recommend a diet that will introduce all of the important nutrients to your body. Make sure that you eat enough fresh fruits and vegetables while staying away from saturated fats and sugars.
  • Watch your calorie intake – Do not believe people saying that you are now eating for two. Although you now need more calories than usual to go through the day, that difference is only among 300 to 400 calories more. Anything above 1,700 calories on a daily basis during your pregnancy puts you on the risk of obesity and all of the complications that come with it. 
  • Exercise regularly – A regular physical activity is a must during your pregnancy. It will keep you healthy, relaxed, and keep you as far as possible away from the risk of obesity. We recommend running, jogging, fitness exercises and yoga during pregnancy. Keep away from lifting weights or anything too extreme, especially during the first trimester.
  • Keep hydrated – Drink enough water throughout the day. It will keep you alert, hydrated and healthy and your body will thank you for it. Make sure that you drink at least eight glasses of water every day and avoid any fizzy drinks, and drinking too much caffeine. 
  • Keep away from alcohol – Alcohol brings many potential risks to you and your baby. Although some alcoholic drinks are considered to have health benefits, we recommend staying far from anything that contains alcohol during the nine months of pregnancy. You will improve your health, your baby’s health and it will be easier for you to maintain a healthy weight during the pregnancy.
  • Get enough sleep – Make sure that you sleep at least 8 to 9 hours each day to repair the damages that have been done to your body the previous day. In addition, staying up too late, snacking on anything that you might find laying around and losing valuable hours of sleep has its price on your health for sure. 


Maintaining a good, healthy body weight during pregnancy will probably prove to be harder than expected. Pregnancy cannot go by without any weight gain, but it can for sure be within the limits of what is considered to be healthy. With a healthy diet, enough water and physical activity, among the other factors, maintaining a good weight should not be a big problem for you. But perhaps you can try and use a little help in the process, or not? 

Phentermine, the best weight loss drug in the United States, might be the best treatment for obesity, but it is sure not recommended to be used during pregnancy and the breastfeeding period. Due to the lack of scientific studies on the topic, Phentermine is not recommended to be used during pregnancy since its potential side-effects on the mother, and the baby is yet to be discovered. Please consult your doctor before proceeding to use Phentermine during your pregnancy.




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