Phentermine (A complete guide)

Phentermine is a prescription drug that is used for weight loss. 

Phentermine is similar to an amphetamine and decreases appetite.

What is phentermine?

Phentermine is similar to amphetamine. It stimulates the central nervous system (nerves and brain), which increases your heart rate and blood pressure and decreases your appetite.

Phentermine is used together with diet and exercise to treat obesity, especially in people with risk factors such as high blood pressure, high cholesterol, or diabetes.

Someone taking Phentermine shouldn’t only rely on the medication they take, but simultaneously practice a heart healthy diet.

Is phentermine legal?

Phentermine is still available by itself in most countries, including the UK in private slimming clinics and in the US.

However, because it is similar to amphetamine, it is classified as a controlled substance in many countries.

Internationally, phentermine is a schedule IV drug under the Convention on Psychotropic Substances.

It was banned in the UK in 2000, but this has since been overturned for private health clinics, strictly prescription only.

But it is not available on the NHS.

How does phentermine work?

It is not fully known how this medication helps people to lose weight.

It may work by decreasing your appetite, increasing the amount of energy used by your body, or by affecting certain parts of the brain.

This medication is an appetite suppressant and belongs to a class of drugs called sympathomimetic amines.

Many people worry about why can’t they loose weight. And the reason for this query is because they lack a healthy diet and lifestyle.

Medicines like these do help in weight loss but only if one follows a proper lifestyle routine.

How do you take phentermine?

Phentermine should be taken by mouth, strictly as directed by a medical or health professional, usually once a day, one hour before breakfast or one to two hours after breakfast.

If needed, your health advisor may adjust your dose to take a small dose up to three times a day.

Carefully follow your professional advisor’s instructions. Taking this medication late in the day may cause insomnia.

If you are using sustained-release capsules, the dose is usually taken once a day before breakfast or at least 10 to 14 hours before bedtime.

Swallow the medication whole. Do not crush or chew sustained-release capsules.

Doing so can release all of the drug at once, increasing the risk of side effects.

If you are using the tablets made to dissolve in the mouth, the dose is usually taken once a day in the morning, with or without food.

First, dry your hands before handling the tablet.

Place your dose on top of the tongue until it dissolves, then swallow it with or without water.

Phentermine is used together with diet and exercise to treat obesity.

The dosage is based on your medical condition and response to therapy.

Your medical professional will adjust the dose to find the best dose for you.

Use this medication regularly and exactly as prescribed in order to get the most benefit from it.

To help you remember, take it at the same time(s) each day.

This medication is usually taken for only a few weeks at a time. It should not be taken with other appetite suppressants.

The possibility of serious side effects increases with longer use of this medication and use of this drug along with certain other diet drugs.

What are the warnings about taking phentermine?

Like other prescription weight-loss drugs, phentermine is intended to be used as part of an overall weight-loss plan.

It is indicated for people who are obese, and who have failed to lose enough weight with diet and exercise alone.

It is not for people who want to lose just a few pounds.

You should not use phentermine if you are allergic to it, or if you have:

·       a history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke)

·       severe or uncontrolled high blood pressure

·       overactive thyroid

·       glaucoma

·       extreme agitation or nervousness

·       a history of drug abuse

·       if you take other diet pills.

What are side effects of phentermine?

If patients suddenly stop using this medication, they may have withdrawal symptoms such as depression or extreme tiredness.

To help prevent withdrawal, a doctor may lower the dose slowly.

Withdrawal is more likely if the patient has used phentermine for a long time or in high doses.

Keep your medical professional informed immediately if you have withdrawal.

Side effects can also include:

·      dizziness

·      tingling in hands or feet

·      dry mouth

·      insomnia

·      short temper

·      nausea and vomiting

·      diarrhea or constipation.

Remember that a patient’s doctor will have prescribed this medication because he or she has judged that the benefit is greater than the risk of side effects.

Many people using this medication do not have serious side effects.

This medication may raise the blood pressure.

Patients should check their blood pressure regularly and inform their medical professional if the results are high.

Health professionals should be informed immediately if any of these unlikely but serious side effects occur: fast/irregular/pounding heartbeat, mental/mood changes (e.g., agitation, uncontrolled anger, hallucinations, nervousness), uncontrolled muscle movements, change in sexual ability/interest.

Can you get addicted to phentermine?

Though it helps many people, this medication may sometimes cause addiction.

This risk may be higher if someone has a substance use disorder such as overuse of or addiction to drugs/alcohol.

Dosage should not be increased or taken more often or used for a longer time than prescribed.

When directed to do so, patients should stop taking this medication.

It is expected that you will lose 5% of your initial body weight on phentermine, but over 12 weeks it can be as high as 10%.

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Frequently asked questions (FAQs) about phentermine: 

1.    What does phentermine do to the body?

Phentermine is an appetite suppressant that is used together with diet and exercise to treat obesity in people who have high blood pressure, high cholesterol, or diabetes. It works by affecting the central nervous system (CNS). 

2.    How much weight can you lose on phentermine?

It is expected that you will lose 5% of your initial body weight on phentermine, but over 12 weeks it can be as high as 10%. 

Is it dangerous to take phentermine?

Phentermine is meant for short-term treatment.

If you do not take it as prescribed, you may be at serious risk.

If you stop taking the drug or do not take it at all, you may not lose weight.

If you take too much, you can have dangerous levels of phentermine in your body. 

How long can you take phentermine for?

Phentermine is usually used for weight loss for a duration of three to six weeks.

The length of the treatment depends on how the patient responds to the medication.

Phentermine can be habit-forming, so it is imperative to take it exactly as described.

It should not be taken at a larger dose, more often, or for a longer period than your doctor prescribes.

What should you not take with phentermine?

You should not consume any other medication that is a central nervous system depressant while you are taking phentermine because this can work against the desired effect of the medication.

This includes alcohol. Combining phentermine with alcohol can increase the risk of side effects from the drug including stomach issues and diarrhea.

6.    Can you drink caffeine while taking phentermine?

It is not recommended to consume caffeine while taking phentermine.

Side effects from phentermine may get worse if it is combined with caffeine.

This includes nausea, nervousness, heart palpitations, difficulty sleeping, tachycardia (rapid heartbeat), and other unpleasant side effects. 

7.    Does phentermine increase metabolism?

Phentermine works by increasing the release of neurotransmitters that stimulate metabolism and suppress appetite.

A neurotransmitter is a chemical messenger that relays information to other neurons to control behavior, mood, appetite, sleep, and so on.

Phentermine is considered a “sympathomimetic” medication because it stimulates the release and inhibition of certain neurotransmitters in the brain. 

8.    How quickly does phentermine work?

After phentermine is taken, it gets absorbed through the gastrointestinal tract and reaches peak concentrations in the blood in about three to four and a half hours.

The half-life of phentermine is about 25 hours, which is the time it takes for half of the dose to be eliminated from the body.

9.    Does phentermine cause mood swings?

Mood swings can be a side effect of phentermine.

If you are taking phentermine and are experiencing mood swings, call your doctor immediately. 

10.                  Does phentermine cause hair loss?

Weight loss drugs such as phentermine can cause hair loss as a side effect.

Hair loss is not usually listed as a side effect because the dieters that lose their hair are often also nutrient-deficient or have other underlying health conditions that contribute to the hair loss. 

11.                  What kind of drug is phentermine? 

Phentermine, brand names Adipex-P or Lomaira, is a prescription medication that has amphetamine-like properties used to suppress appetite.

It can jumpstart weight loss by decreasing your appetite or making you feel full longer.

12.                  Can you take phentermine at night?

It is recommended to take phentermine with or without food once daily in the morning.

This is because phentermine may cause difficulty falling asleep or staying asleep due to its amphetamine-like properties.

Amphetamine increases energy and heart rate and suppresses appetite.

Phentermine can jumpstart weight loss by decreasing your appetite or making you feel full longer.

If you are interested in learning more about phentermine or other weight loss information try these books:

Safer Than Phen-Fen!

Without a doubt, the prescription-drug combination of phentermine and fenfluramine known as phen-fen has become the most successful medical weight-loss method ever, used by more than 18 million people in the US.

However, while phentermine has been used safely for more than thirty years, a growing body of scientific evidence links fenfluramine to dangerous side effects affecting the heart and lungs.

Similar alarming results are reported with Redux and Pandimin, related weight-loss prescription aids.

Dr. Michael Anchors, a Harvard-trained physician and an expert on treating obesity, has developed a safe alternative.

Using phentermine with other medications in place of fenfluramine, he has helped over 600 people lose more than 10,000 pounds since 1995 — and the vast majority have shown they can keep the pounds off with no more than a minor maintenance program.

In this groundbreaking book, Dr. Anchors spells out his safe, new path to weight loss and better health. 

Qsymia Plan for Weight Loss: A Practical Guide To Using the New Diet Medication

Endocrinologist and weight loss expert, Dr Richard Lipman presents The Qsymia Plan For Weight Loss.

It is to help you get rid of that extra weight now and forever. It is not for the individual that has 10 or 20 pounds to lose but for the 75 million Americans that have 30, 50, or 100 pounds or more to lose who have tried everything and failed.

It is for the millions more with diabetes and other medical problems whose obesity has been impossible to reverse.

It is for those one hundred thousand or more Americans thinking about drastic actions such as gastric bypass surgery.

This revolutionary weight loss plan combines a simple, easy-to-remember food plan with the first of a new class of FDA approved prescription medications that puts you in control of your hunger and cravings, perhaps for the very first time in your life.

The breakthrough drug is Qsymia-a combination of Phentermine and Topamax.

These two medications have been on the market for decades and more than 30 million people have taken phentermine and four million people have been treated with Topamax around the world.

The Qsymia Plan for Weight Loss is the beginning of a new day in the battle against obesity.

Obesity: Evaluation and Treatment Essentials, Second Edition


Obesity is considered a complex and multifactorial disease. Its treatment, therefore, must also be multimodal and tailored to meet the needs of each patient.

Obesity: Evaluation and Treatment Essentials presents a wide spectrum of practical treatment protocols for obesity including exercise, pharmacology, behavior modification, and dietary factors, from the point of view of the practicing physician.

The book includes information about the new pharmacotherapy available for the treatment of obesity.

It also includes a chapter on medical treatment of pediatric obesity that identifies the special needs of children and outlines approaches for managing the obese child.

A chapter on binge eating disorder has been added and the information on pharmacology of bariatric medicine has been updated.

The book addresses various dietary interventions such as low-calorie balanced diets, low-carbohydrate diets, and very-low-carbohydrate diets while also exploring the comorbidities of obesity such as hypertension, cardiovascular disease, and Type II diabetes.


Phentermine – – September 2018

Phentermine HCL – – January 2020

Weight loss – Mayo Clinic – January 2019

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