Report on Phentermine Side Effects and Usage by AskDocWeb

About Phentermine

15 mg Phentermine
  30 mg Phentermine
  37.5 mg Phentermine
  Phentermine Blue

What is Phentermine?

Phentermine (pronounced FEN-ter-meen) is the brand name of the drug phentermine hydrochloride. It’s also sold as Adipex-P, Fastin, Ionamin, Obenix, Obephen, Oby-Cap, Oby-Trim, Panshape M, Phentercot, Phentride, Pro-Fast HS, Pro-Fast SA, Pro-Fast SR, Teramine and Zantryl.

Phentermine is a class of diet pills (all by prescription). It’s an appetite suppressant.

The time release version of Phentermine is sold under the brand name Ionamin.

Both Phentermine and Adipex-P are the immediate release formulas, designed to enter the bloodstream quickly.

The Phentermine diet pill may come in tablet or capsule forms.

The chemical name for Phentermine Hydrochloride is phenyl-tertiary-butylamine hydrochloride. It’s a white crystalline powder, very soluble in water and alcohol.

The inactive ingredients in Phentermine are invert sugar, F D and C Blue 1, methylcellulose, polyethylene glycol, starch, sucrose and titanium dioxide.

The ink used to mark the gelatin capsules is composed of F D and C Blue 1, ethyl alcohol, food grade refined shellac, isopropyl alcohol, n-butyl alcohol, propylene glycol and modified pharmaceutical shellac.

Phentermine is a short-term supplement to be used with a change in diet and the addition of exercise in the treatment of obesity.

These pills and capsules come in varying strengths from 15 mg up to 37.5 mg. And different colors, depending on the manufacturer.

How does Phentermine work?

Simply, it makes you less hungry. It suppresses your appetite possibly by changing brain levels of serotonin.

Phentermine causes elevation of blood pressure, faster heart rate and stimulates the nervous system like the amphetamines. It works by stimulating the hypothalamus and affects certain neurotransmitters that decrease appetite.

What side effects do users of phentermine report?

A few people have mood swings

Elevated blood pressure
Increased blood pressure
Rapid or irregular heart beats
Fatigue (tiredness)

During the first few days you may have dry mouth or an unpleasant taste in your mouth, sleeplessness, irritability, stomach upset or constipation. This is just your body adjusting to the Phentermine. Tell your doctor if these effects persist or become bothersome.

Tell your doctor if you experience


chest pain

breathing difficulties



difficulty urinating



mood changes

nervousness, restlessness or tremor

pounding heart


impotence or changes in your sex drive.

Please note: If you are looking for a female sexual stimulant, we suggest you take a look at Vigorelle rather than using phentermine.

What are the symptoms of overdose or something gone wrong?

Stop taking phentermine and seek emergency medical attention if you experience any of the following:

abnormal behavior


an allergic reaction (difficulty breathing; throat closing up; swelling of your tongue, lips, or face; or hives)




irregular heartbeat



rapid breathing




very high blood pressure (severe headache, blurred vision)


If you have any of the above, seek emergency medical attention.

Storing Phentermine

Store at room temperature in a tightly closed container, away from sunlight and moisture. Remember to keep all medications out of the reach of children.

Conditions you should tell your Doctor about before taking Phentermine:

agitated states

allergic to sympathomimetic amines

anxiety disorder

arteriosclerosis (hardening of the arteries)


cardiovascular disease


emotional problems

epilepsy or another seizure disorder


heart disease

high blood pressure

history of drug abuse




thyroid problems
Seek medical attention right away if you experience any of the following SEVERE side effects occur when using Phentermine: rash, itching, hives, difficulty breathing, tightness in the chest, swelling of the mouth, face, lips, or tongue; bizarre behavior, chest pain, fainting, fast heartbeat, pounding in the chest, shortness of breath, swelling of the legs and feet; and/or tremor.

This is not a complete list of all possible side effects that may occur.

Tell Your Doctor if you are taking any of the following medicines:

amitriptyline (Elavil)
amoxapine (Asendin)
Any medicine, prescription and non-prescription
clomipramine (Anafranil)
desipramine (Norpramin)
doxepin (Sinequan)
high blood pressure medicine
imipramine (Tofranil)
MAO inhibitors
monoamine oxidase
nortriptyline (Pamelor)
protriptyline (Vivactil)
tricyclic antidepressant

Things to avoid while taking Phentermine

Use caution when driving, operating machinery, or doing anything hazardous. Phentermine may cause dizziness or blurred vision, and it may hide the symptoms of extreme tiredness.

Don’t take it late in the day. Taken too late in the day may cause insomnia.

What happens if I miss a dose?

You should be taking Phentermine before breakfast. If you miss a dose and remember before 3:00 or 4:00 PM, go ahead and take it. Taking it too late in the day will cause you insomnia. Do NOT take two in one day.

General Notes on phentermine

Be extra cautious when driving, operating machinery, or performing any hazardous activities until you know how this drug affect you.

Avoid “stimulant” drugs that may increase your heart rate or blood pressure such as caffeine and decongestants. Common over-the-counter cough and cold medicines contain decongestants.

Phentermine is not recommended for use in children under 16 years of age.

Adipex-P is the most popular brand name of phentermine.

Phentermine is the basic tool for losing weight used by many weight loss programs.

Phentermine and fenfluramine together are popularly known, advertised and referred to as “Fen-Phen.”

Fenfluramine and phentermine were not designed for use for more than a few weeks.

The number one weight loss medication in the USA is Phentermine.

Weight loss improves diabetes control and decreases blood pressure, cholesterol levels.

Phentermine should only be used in with a well planned daily exercise routine.

Other popular weight loss drugs include Xenical and Meridia. These drugs will work for many people, but Xenical does have side effects that can be unwelcome.

Don’t share any prescription medication with others. In most places that is a crime.

Phentermine is habit forming, both physically and psychologically.

If you use it continuously for several weeks, you may experience withdrawal effects if you stop taking it suddenly. Talk to your doctor about how you should go about stopping this medication.

Phentermine is taken 30-60 minutes before breakfast, on an empty stomach.

Phentermine tablets or capsules should be swallowed whole. Don’t crush or chew them.

It’s not known if phentermine passes into breast milk. If you are breast-feeding a baby, it is better to error on the side of safety and avoid it.

Take each Phentermine tablet or capsule with a full glass of water.

You must remember to lower your overall consumption of food for Phentermine to be effective.

Phentermine will increase your energy levels.

This medication may lower your potassium level.

The ideal time length for taking Phentermine is four weeks, then take a break.

You need a prescription in order to use Phentermine.

Phentermine decreases in effectiveness over time. You can start seeing benefits again if you stop taking it for awhile.

Please note that as of February 22, 2012, the FDA has changed the pregnancy category for Phentermine from C to X because animal or human studies have shown that the risk of adverse effects on a fetus outweigh any benefit.

The trademarks used on this website remain the property of the individual trademark owners. The use of such trademarks are intended only to identify products by their common name.

Common Misspellings for Phentermine

Phentermine is often misspelled, as many people hear the word verbally, write it down and spell it incorrectly. Here are a few of the most common misspellings for Phentermine: Phetermin, Phetremine, Fhentermine, Phen Phen, Fentermine, and Fentermin.

Phentermine Feedback

Use this discussion forum to share your experience with Phentermine side effects. What would you tell your best friend about this product? Please remember that we do not give medical advice. That is for your local health care provider, who is familiar with your medical history. You can use the form below to add your comments,
feedback or Phentermine review.

Phentermine withdrawl symptoms

Can withdrawl symptoms of Phentermine include being tired and having blurry vision and feeling really out of it? How long do these withdrawl symtoms last and is there anything I can do to make it better. Thanks


AskDocWeb: A few things you can do like eating more fruit and drinking plenty of liquids will help your body clean itself. If symptoms persist, see your doctor.


A few years ago, I took fen-phen for about 6 months. I was never tested to make sure that everything was okay. Now I am taking Phentermine. How safe is this drug considering I had been on the fen-phen in the past? Does is increase my chances of health problems? Has anyone ever reported any serious health conditions or possibly death?


AskDocWeb: Some side effects of Phentermine are potentially serious. If you experience any of the following side effects, do not hesitate to seek medical attention. They include behavioral changes, fainting, pounding in the chest, chest pain, rapid heart beat, tremors, swelling in the legs or feet and fainting.

A small percentage of patients may experience some adverse, cardiovascular side effects. The most common is an increase in heart rate. Phentermine may also cause hypertension and arrhythmias in certain people.

As with any drug there is a possibility of an allergic reaction. The signs of an allergic reaction to phentermine include itching, difficulty breathing, rash, hives, swelling of the lips, tongue, face or mouth and tightness in the chest.


Hi, I just started to take this medication, but im wondering if it is okay for me to combine my cold medicine with it? I just started to get a cold and need to take some night quil and day quil, so now im not sure if these medicines will cause any adverse reactions, such as increase my blood pressure more ect….please let me know.

Thank you.


AskDocWeb: The patient information for Phentermine says to avoid “stimulant” drugs that may increase your heart rate or blood pressure such as caffeine and decongestants. Many common over-the-counter cold medicines contain decongestants. And yes, Phentermine may elevate blood pressure.

Phentermine Feedback
Date: 3/23/2003

I was just wanting to say that I have been on Phentermine for five weeks and so far, it has really cut down my appetite. I have never been over two hundred pounds in my life. I have already lost over 12 pounds and I’m not even having to starve myself like I usually do when trying to lose weight. So I already see the difference in my appearance, plus I have already went down a whole size in clothes. Thanks for listening.


Date: 4/8/2003

I was wanting to know if there are any damages that can be done to your liver if you have taken phentermine off and on for several years. Or is there any harm to your reproductive organs if you have taken it for several years.


AskDocWeb: While we haven’t found evidence of either, that is not conclusive evidence. Some of the drugs we did find that may cause liver damage include Acetaminophen, Duract, Rezulin, Trovan, Rezulin® and Posicor. In rare cases, fluconazole and Lamisil have caused liver damage.

The early signs of liver damage are nausea, vomiting, abdominal pain, unusual fatigue, loss of appetite, yellow skin or eyes, itching, dark urine, or clay colored stools. These symptoms may be something else but, if you have them, you should notify your doctor immediately.

To settle your mind, you could have your liver tested. A liver function test is a blood test that can detect several kinds of liver damage. There are two types of the test. One test indicates the enzyme levels of the liver. The other is used to assess whether the blood clots properly.

Results with Phentermine
Date: 5/20/2003

I lost 35 pounds in 7 weeks with Phentermine and the results are amazing, I am very happy and content. I would highly recommend it to anyone.


Click here for more feedback from users.

Most recent post: June 22, 2017

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