Is Phentermine an Amphetamine like Crystal Meth?

Dr Covington answers your questions.

No. It is not.

Phentermine is not an amphetamine, it is “amphetamine-like” meaning that it can bind to the same receptors in the brain and has a few similar actions but it is not the same as crystal meth or any drugs in the amphetamine class.

The major difference is the release of dopamine is much less with phentermine than the drugs in the amphetamine class and this is also why phentermine is not addictive like methamphetamine and cocaine.

The chief neurotransmitter released with phentermine is norepinephrine and serotonin to a lesser extent, there is also minimal dopamine released.

The appetite suppressing effects, increase in energy, potential insomnia are similar for phentermine and amphetamine.

We discuss how phentermine works in more detail along with other weight loss medications in this blog article (read here) → FDA Approved Weight Loss Medications & How They Work


Check out my Youtube Videos on Phentermine (below): 

How Phentermine Works 

Most Common Mistake Patients make with Phentermine


Dr Covington

weight loss medicine

FDA Approved Weight Loss Medications & How They Work

Over 75% of Americans are overweight with over 30% obese; therefore, weight loss solutions are imperative. A bariatrician is a medical doctor who treats patients with excess fat and diseases related to extra weight such as high blood pressure and joint pain. In addition to nutrition, physical activity, and behavioral health, a bariatrician often uses FDA approved weight loss medications as a treatment for obesity. Obesity is not only the most common medical condition that adult patients share but it is also linked to deadly diseases such as heart disease, fatty liver, and various cancers. Unfortunately, obesity is severely under treated and as a result many individuals resort to ineffective or dangerous methods for weight loss. In most cases if a doctor prescribes one of these medications for weight loss it is because the risk of overweight or obesity outweighs the risk of the medication. This article discusses safe and effective FDA approved weight loss medications and how they work. Why FDA Approval Matters The Federal Drug Administration (FDA) is a government agency that regulates medications prescribed in the United States for safety and efficacy (or effectiveness). All medications have side effects; however, drugs approved by the FDA are studied for several years in volunteer patients to determine how they work and the most common side effects. Several medications require additional testing even after FDA approval. FDA approved weight loss medications must demonstrate more weight loss when compared to diet and exercise alone and/or a placebo. On the contrary, non-FDA approved substances have not been tested under strict regulatory guidelines and have not been required to show superior results to placebo or diet and exercise alone. weight loss center in charlotte nc How Much Weight Will You Lose? The amount and rate of weight loss depends on the medication, the starting weight, the individual, and how well one follows proper nutrition and physical activity recommendations. On average, weight loss medications will yield twice the amount of weight loss when compared to placebo and diet and exercise alone. In the case of “resistant weight loss” sometimes a weight loss medication is the only way people are able to successfully lose weight despite their best efforts. The amount of weight loss can range anywhere from 20-40 pounds to over  100 pounds and depends on the amount of excess fat on the body. In addition, weight loss medication can be used after bariatric surgery for patients who experience weight regain. What is the criteria for weight loss medication? In order to qualify for a weight loss medication, you must have a Body Mass Index (BMI) greater than 30 or a BMI greater than 27 (overweight category) with at least 1 weight related co-morbidity (such as sleep apnea, joint pain, or diabetes). The BMI is the ratio of weight to height and can be over-estimated for individuals with a lot of muscle mass or underestimated for individuals with a low body weight and high body fat percent (since it does not account for body composition). You can calculate your BMI using our BMI Calculator on the bottom right corner of the website's home page.
Underweight Below 18.5
Normal Weight 18.5-24.9
Overweight 25-29.9
Obese 30-49.9
Morbidly Obese 40 -49.9
Super Obese 50-59.9
Super Super Obese 60 and Above

FDA Approved Weight Loss Medications

#1 Phentermine - Adipex, Suprenza, Lomaira

 Phentermine is the #1 prescribed weight loss medicine in the United States and was first approved in 1959. Phentermine is popular for it’s appetite suppression and energy producing effects that lead to weight loss. Phentermine comes in the form of a tablet, capsule, or disintegrating pill (Suprenza) and works by releasing norepinephrine; a brain chemical that can reduce food intake, increase energy and metabolism, and break down fat. The medication is taken in the morning because it can cause insomnia or difficulty sleeping. The most common side effect is thirst from dry mouth; however, phentermine can also cause feelings of nervousness, increased heart rate, heart palpitations, increased blood pressure, chest pain, headache, and dizziness.

Phentermine is not safe for everyone, especially those with a history of heart disease, therefore, a prescription from a doctor is required along with routine monitoring.

Lomaira is a special formulation of phentermine in a low dose. It may be better tolerated due to the smaller dosage and can be taken up to 3 times a day.

 Check out Dr Covington's Youtube Videos on Phentermine 

Phentermine and How it Works

Most Common Mistakes People Make with Phentermine

#2 Qsymia (phentermine and topiramate)

Qsymia was FDA approved in 2012 and is the combination of two medications that both impact weight loss separately. Phentermine is an appetite suppressant while topiramate aids in binge eating and cravings; the combination of these two medicines enhances weight loss results. Topiramate is also used to treat seizure disorder and migraine. In clinical studies, Qsymia demonstrated an average weight loss of 8.5% when compared to placebo, with almost half of the patients losing more than 10% in the first few weeks.  Qsymia should not be taken by pregnant women or women seeking to get pregnant (this is common for all weight loss medications) and can cause dizziness, constipation, numbness, unusual taste, dry mouth, difficulty sleeping, and changes in mood. Women of childbearing age are strongly recommended to take a monthly pregnancy test and use birth control or barrier protection when taking this medication.

Check out Dr Covington's Youtube Video discussing Qsymia and How it Works

#3 Belviq and Belviq XR (lorcaserin)

Belviq is a weight loss medication approved in 2012 that causes a release of serotonin in the brain. Belviq comes in 2 forms, one is immediate release that is taken twice a day and the other is extended release and can be taken once a day. Belviq works by reducing appetite, hunger, and cravings along with the ability to get full quicker with less food. Common side effects are dizziness, headache, fatigue, constipation, diarrhea, nausea, and dry mouth. Belviq may also benefit patients with obesity and diabetes as it demonstrates an independent ability to reduce hemoglobin A1c, a lab value used to determine the severity of diabetes.

phentermine in charlotte

 #4. Contrave (naltrexone and bupropion)

This weight loss pill is comprised of two previously approved drugs, naltrexone and bupropion. Buproprion is used for depression and smoking and has been shown to reduce hunger and aid in weight loss. Naltrexone is used for alcohol cessation but enhances the effect of bupropion by adding to the reduction in hunger and cravings. Contrave was approved in the United States in 2014. Clinical trials demonstrate that close to 50% of patients lost at least 5% of their excess weight when compared to placebo. Like Qsymia, Contrave follows a weekly titration until reaching the target weight loss dose. Contrave can increase heart rate (2-3 beat per minute) and cause constipation and diarrhea, headache, dizziness, insomnia, nausea, vomiting, and dry mouth, and should not be used in anyone with a history of seizures of liver disease.

#5. Saxenda (liraglutide)

 Saxenda, approved in 2014, is unique from the other weight loss medications in that it is an injection of a “biologic” that must be refrigerated, whereas the other weight loss medications are pills. Saxenda is a glucagon-like peptide-1 (GLP-1) product which means it is a satiety hormone that is already produced in the body. Saxenda works by enhancing satiety and helps individuals feel full and eat less calories. The medication is injected once a day in the abdomen, arm, or thigh and is titrated up over a 5-week period until the top dose is reached. The most common side effect is nausea but can also cause headache, diarrhea, constipation, abdominal pain, and an increase in heart rate.

 #5. Orlistat (Xenical, Alli)

 Orlistat is approved for weight loss and works by reducing the absorption of fat from food. The medication comes in 2 versions, one is Xenical which requires a prescription and the other is Alli (a lower dose) that is available over the counter. The medication can reduce dietary fat absorption by as much as 25%. Orlistat is the only weight loss medication approved for use in children.  The most common side effects are stomach pain and loose stools which can occur with a fatty meal; therefore, patients are advised to eat a low-fat diet to reduce this effect.


#6. Diethylpropion, Benzphetamine, and Phendimetrazine (Bontril)

 These medications are appetite suppressants that work similarly to phentermine but may be tolerated differently based on their chemical structures. All of these medications were FDA approved in the 1960s with the exception of the extended release version of diethylpropion which was approved in 2011. The side effect profiles are similar to phentermine and all can cause dry mouth, insomnia, heart palpitations, dizziness, and irritability.

Weight Loss Medication is Not a Magic Pillhow to lose fat

Weight loss medications are tools for weight loss that serve several purposes. Weight loss medications help with appetite, cravings, energy, and fat loss but they are NOT magic pills! All FDA approved weight loss medications require proper monitoring with a licensed medical doctor and are used along with healthy nutrition and exercise.

phentermine doctor in charlotte

Most Common Mistakes People Make with Phentermine

Phentermine is an FDA approved weight loss medication that is used to control appetite, it is approved for individuals with a body mass index (BMI) that meets medical criteria for obesity – a BMI over 30 kg/m2 or a BMI over 27 kg/m2 with obesity related medical conditions such as high blood pressure, sleep apnea, or weight related joint pain. Phentermine effectively reduces hunger, cravings, and increases metabolism and for these reasons phentermine is a popular medication used for obesity and medical weight management. Phentermine is the oldest and arguably one of the most effective weight loss medications on the market, to add, it is the cheapest weight loss medication and therefore easy to access in most pharmacies across the country. Phentermine is the most commonly prescribed weight loss medication in the United States, however, despite phentermine’s vast use and longevity on the market there are common mistakes that patients make that can reduce short and long-term weight loss success.

Not Eating Enough and Skipping meals


I know what you’re thinking, isn’t the point of phentermine to NOT eat? No, it’s not. This is one of the biggest misconceptions with phentermine. Phentermine is not a starvation pill! The purpose of phentermine is to help control weight gaining signals in the body such as uncontrolled appetite, excess hunger, increased fat storage, poor food choices, and slow metabolism to aid in weight loss. Phentermine’s primary mechanism of action is to reduce appetite, however, not eating or skipping meals is not the goal and will lead to more problems in the long run. Many are aware that muscle weighs more than fat, when we lose muscle during a starvation or restriction diet it can be very exciting to see large weight loss on the scale, however, the muscle loss will eventually turn into a reduction in basal metabolic rate (BMR) which will make future weight gain easier. This is one phenomenon that can occur when patients misuse phentermine, they lose large amounts of weight to only gain it all back in a few months.

The next reason for Proper nutrition is imperative for all human beings, we all need the right combination of micro and  macronutrients in order to survive, using phentermine to aid in starvation is not the right method for weight  loss, primarily because it will not last beyond a few months and additionally because it can lead to poor nutrition and Many people using phentermine tend to make the mistake of starving themselves for too long, thinking this will stimulate the weight loss process.

Poor Diet and Improper Nutrition


Nutrition is the nourishment for humans responsible for health, wellness, and growth. The body needs nutrition. There are different schools of thought on the amount, timing, and type of nutrition but the one thing that we can all agree on is that a body lacking proper micro and macronutrients will not survive.

Poor or malnutrition can range from inadequate vitamins, minerals, micro and macronutrients to excess “bad” or toxic foods that can lead to various diseases and increased morbidity. Phentermine is a tool that helps reduce the intense hunger and many of the cravings for the wrong foods that lead to weight gain so that individuals can focus on the right foods, smaller portions, and proper nutrient balance. Proper nutrition will not only maximize weight loss results, increase energy and overall performance, but will reduce nutritional deficiencies, fatigue, and the rebound hunger and cravings that occur as a result of “crash diets”

Overestimate Phentermine


FDA approved weight loss medications are great tools; however, they are not magic pills. There is no magic, all weight loss occurs from controlling negative physiology that leads to weight gain and introducing positive habits and physiology centered around weight loss. Weight loss physiology involves more than just diet and exercise, there are multiple factors such as proper stress management, sleep, hormonal balance, environment, emotions, and many more. When individuals overestimate the effect of phentermine they are setting themselves up for disappointment. The medication has a wide range of effectiveness that is dependent on the person taking the medication along with their medical and obesity history, habits, other medications, and various other factors. Phentermine does not work for everyone, although there are individuals who will have a great response with phentermine for several months there are some who will have absolutely no response with phentermine, others who will have minimal to limited effect, and several who will have an effect that may quickly wear off. Phentermine works best in coordination with a proper diet and adequate physical activity, taking phentermine without changing poor habits will not create long-term weight loss and will increase the likelihood of future weight regain.

Taking Phentermine at the Wrong Time


Phentermine is a once a day medication that should be taken first thing in the morning. Taking the medication on an empty stomach or with food is not as important as making sure to take it early in the day. One of the side effects of phentermine is energy and focus which can lead to insomnia or trouble sleeping. The likelihood of insomnia increases the later in the day that the medication is consumed. It is important to that the medication in the morning so that sleep quantity and quality is uninterrupted, it’s important to remember that proper sleep is equally effective for weight loss.

Skipping or Forgetting to take Phentermine


It is important to take all medications as directed by the doctor, phentermine is no different. Taking phentermine daily especially in the beginning is very important. While phentermine is aiding in appetite reduction, increased metabolism, and elevated energy, stopping the medication or skipping phentermine can have the opposite effects. Premature discontinuation of phentermine may lead to intense hunger, cravings, and fatigue.

Phentermine is a great tool for managing and treating the disease of obesity, however, it is imperative to use under direct supervision of a physician or medical weight loss doctor and as directed with a comprehensive weight loss program.


Want to learn more?


Watch Dr Covington’s video discussing the most common mistakes people make with phentermine

Watch Dr Covington’s live video discussing phentermine and how it works


phentermine blog pic-min

How Phentermine aids in Weight Loss

Phentermine or Adipex is commonly used for weight loss in combination with diet and exercise. Although phentermine is one of the oldest FDA approved weight loss medications on the market there are still a lot of questions regarding its safety and efficacy. Does phentermine work long term?  Is phentermine necessary for weight loss? Is phentermine safe? All of these questions are valid. To answer these concerns along with how the most commonly prescribed weight loss medication in America aids in weight reduction we will explore a few key factors, starting with phentermine’s mechanism of action.

How Phentermine Works

Phentermine is a medication that is only available by prescription. It requires physician monitoring because it is categorized as a “controlled substance”. Phentermine is not a magic pill, it is simply a tool used to help with weight loss. The mechanism of action for phentermine causes a release of norepinephrine from the brain. Norepinephrine (also known as adrenaline) is a natural neurotransmitter produced and released in the body. This chemical is present when we are afraid, nervous, or involved in an action that requires energy, such as moderate to rigorous exercise or running from a bear (hopefully the latter never happens). As luck would have it, the release of norepinephrine from the brain also happens to promote several weight reducing activities such as appetite suppression, heightened attention and awareness, increased circulation of oxygen and nutrients throughout the body and increased metabolism. The increased oxygen circulation increases oxygen supply to the brain, which allows for rapid decision-making, and the activation of large skeletal muscles, which allows us to run from danger if necessary. This cascade of events is called the “fight or flight” response.

In addition to appetite suppression, norepinephrine reduces the thoughts, obsessions, and preoccupations with food. This is why some individuals taking phentermine may forget to eat because they don’t even think about food anymore. The metabolic increase from norepinephrine causes an increased use of stored body fat and an increased uptake of calories at rest in a 24-hour period.

If you are wondering why we don’t experience weight loss on a normal daily basis due to this presence of norepinephrine, it’s simply because norepinephrine only sticks around for a few seconds before it is broken down by the body.

Now that you understand how norepinephrine works, you also understand how phentermine works, it causes a release of norepinephrine and therefore turns on fat burning and counteracts the body’s natural resistance to weight loss.

How much weight will you lose on phentermine?

For all FDA approved weight loss medications, results will vary. On average individuals using phentermine can expect to lose twice the amount of weight that they would lose with diet and exercise alone. This means that if the average rate of weight loss is 8-10 pounds a month that a patient on phentermine may lose twice this rate, 16-20 pounds a month. This is of course considering that there are no counteractive medications, medical conditions, or other hindrances.  It is normal for the weight loss seen in the first few weeks to slow down to a more steady pace over time. This will occur even more for individuals closer to ideal weight. The most significant results, however, are those witnessed by the truly weight loss resistant. This is the individual who fails to lose weight despite multiple attempts over an extended period of several years. For this individual, phentermine can be the catalyst to finally turn on fat burning and when this occurs any weight reduction is extraordinarily significant!

What not to do on phentermine – the “Phentermine Commandments”

  • Thou shalt not skip meals
  • Thou shalt not severely restrict calories
  • Thou shalt not rush the process
  • Thou shalt not ignore nutrition and macronutrient balance
  • Thou shalt not ignore physical activity
  • Thou shalt not skip doctor’s appointments or routine monitoring


Despite the weight loss achieved while taking phentermine resist the urge to skip meals or severely restrict calories because this will only backfire long term. Also resist the urge to speed up weight loss results or create unrealistic demands. Keep in mind that phentermine is a weight loss tool, not a Genie in a Bottle, you cannot expect to lose all of your excess weight overnight.

What to expect when starting phentermine? Is phentermine safe?

Phentermine, like any medication, is safe when used for the right patient and when prescribed by a knowledgeable and experienced physician. Many medications can be refilled without routine check-ins with the doctor, however, phentermine is not one of those medications. Phentermine requires routine monitoring, physical examinations, vital sign checks, and regular office visits to discuss side effects.

What are the most common side effects for phentermine

The symptoms caused by phentermine will vary according to the patient but the most common side effects are appetite suppression and thirst. Thirst can occur as early as the first day and is easy to fix by simply drinking plenty of water. Other common symptoms are increased energy which can lead to insomnia or trouble sleeping. For this reason, it is recommended to take phentermine first thing in the morning. Thirst and insomnia typically subside after the first few weeks but for individuals with severe insomnia your doctor may decide to avoid phentermine altogether. Phentermine can also increase anxiety and other mental diseases such as bipolar disorder. Lastly, the most significant side effect of phentermine is an increase in heart rate and blood pressure along with heart palpitations. All of these symptoms along with other less common side effects not mentioned in this article must be monitored by a doctor.

Is phentermine addictive?

The short answer is not typically. Phentermine is in the class of medications known as amphetamines due to it’s chemical structure and action in the brain. However, it is not a chemical that patients typically get addicted to. Individuals who have successfully lost weight with phentermine may develop a psychological dependence, meaning they may emotionally feel fearful of regaining weight off the medication or feel like they are unable to make healthy decisions without taking phentermine. Some may even notice a physical increase in hunger and cravings once no longer taking the medication.

Will phentermine stop working over time?

It depends. For some people the answer is yes, after several months appetite suppression will subside.  For others, the effects of phentermine remain for a much longer period. Phentermine is not effective for everyone. If phentermine is ineffective for weight loss, meaning an extensive plateau, lack of appetite suppression, or minimal to no weight loss results over an adequate period, it should be discontinued. In this event, a weight loss doctor like Dr Covington can recommend an alternative treatment or FDA approved weight loss medication for you.

Phentermine requires a comprehensive weight management plan

This medication promotes weight reduction by providing energy, focus, suppressing food intake and reducing the desire to eat. Individuals undergoing a weight loss plan are able to make healthier food choices and pursue physical activity without hunger and fatigue. However, this medication is most effective when combined with a comprehensive weight management plan that includes medical oversight, nutrition, physical activity, and routine medical monitoring.

Want to learn more? Watch Dr Covington’s live video discussing phentermine and how it works.