How long does Phentermine stay in your system?

In this blog we will read “How long does Phentermine stay in your system?”

I wake up one day to realize I can eat whatever, whenever without getting fat?

Doesn’t it sound like a dreamy affair, well this is a reality for some but only a dream for most of the people out there.

In the modern times, when looking fit is much more important than being fit, people try different ways, some go for dash diets, while some spend hours in the gym, some go for intermittent fasting, some go for a run.

People tend to forget the true meaning of health.

“Being healthy is a state of complete physical, mental and social well-being and not merely the absence of disease and infirmity”, as stated by WHO (World Health Organization).

But instead of focusing on all the domains, that is, physical, mental, and social, people tend to focus only on one, physical.

And in this rat race where millions are participating to look good, many experiments are also tried and tested and if they worked, they are used, sometimes under the table as well.

One such experiment is Phentermine.

Let’s talk about Phentermine and how long it stays in our body and what it can do for you.

What is Phentermine?

Phentermine is a central nervous system stimulator which increases heart rate and blood pressure and depresses appetite. It is one of the most prescribed medicines for weight loss. It is given in combination with other drugs as well to increase its effect.

How long does Phentermine stay in your system?

It was very popular in the USA for its weight loss and fat burning properties and it was mixed with other drugs as well but because of its side effects its use was restricted.

But still Phentermine is available on prescription. Many people take it without prescription including many celebrities as well.

After 12 weeks of usage it’s effect starts to diminish but in the beginning it’s a great way to kick-start weight loss when combined with proper diet and exercise.

How long does Phentermine stay in your system?

Phentermine has a half life of approx. 24 hours that means it stays in the body for four days.

Well, that’s not the case every time. The half life and the effect of Phentermine also depends on the frequency, dosage and any other substance or drug consumed along with Phentermine. 

Other factors like the kind of diet taken, exercise also contribute to it.

It remains in the body fluids like saliva, urine, blood, in the hair and can be detected on a drug test.

Though it can be detected in the body for 5-6 days but it’s effect is short acting and lasts for only 9-12 hours.

In the Urine

Urine is one of the commonly used body fluid taken into account for detecting the presence of Phentermine.

Phentermine can be detected in the urine for 48 -72 hours but can be found after that as well in several cases.

In the Blood

In the blood it stays for around 24 hours but can be found after that as well in some cases.

In the Hair

In other tests where Phentermine stays for several days, in hair follicles which can provide a lot of information about the body, Phentermine can be detected for up to 90 days.

Any body hair can be used and not necessarily scalp hair. Any styling products used or dye cannot affect the presence of drug.

In the Saliva

It can be detected in the saliva for 24 – 48 hours from the time of last dosage.

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Why is it used?

  • It is used to suppress appetite and makes you feel full for longer.
  • It is prescribed along with dietary changes and exercise.
  • It is prescribed for people who are not able to reduce weight despite diet and exercise.

Side effects of Phentermine

how long does phentermine stay in your system?

Phentermine can be considered as a magic pill for weight loss when combined with diet and exercise. It shows quick results but also it’s effects starts diminishing within few weeks. 

It should be only used for short term as it can be addictive. But, this is not the only side effect of Phentermine.

Let’s see other common and severe side effects of Phentermine.

Common side effects of using Phentermine are:

  • Itching
  • Dry mouth
  • Constitution
  • Stomach pain
  • Dizziness
  • Decreased libido

Following are the severe side effects of Phentermine and consult to your doctor if you experience them:

  • Chest Pain
  • Pedal Edema
  • Tachycardia
  • High blood pressure which can cause epistaxis (nose bleeding), headaches
  • Insomnia
  • Shortness of breath
  • Mood swings

Withdrawal symptoms

Phentermine is an addictive drug and the body can show symptoms of addiction when the patient withdraws the usage of Phentermine.

These withdrawal symptoms can influence the patient to continue using the drug in order to not experience those symptoms and if the patient is taking it without prescription then he/she may continue to take it any dosage, for longer durations without knowing the fact that after weeks it stops showing the weight loss property it once had.

These withdrawal symptoms include:

  • Craving 
  • Thinking about taking Phentermine
  • Nausea
  • Diarrhea/ Constipation
  • Excessive sweating
  • Heart palpitations

So, if the body is showing these symptoms then, it is likely that the person is addicted with Phentermine and need to consult the doctor immediately whether you are taking the medication by doctor’s prescription or under the table.

Lose weight the right way

I am aware that losing those extra pounds and looking good is everyone’s dream but it is not necessary to choose the wrong way for that.

It is essential to do things the right way to make things right.

Here are the steps you can follow not only for a good body weight but also for a better lifestyle:


how long does phentermine stay in your system?

BMI stands for body mass index which can tell if a person falls under the category of healthy or not in terms of their weight.

It is calculated by taking into account two things which are height and body weight.

Know you correct BMI to get a clear view on how much you are supposed to lose and what will be the ideal weight range for your body type.

Make a schedule

Making a schedule to change your lifestyle is very important.

Changing your lifestyle all of a sudden is not easy and also not a one day thing. One needs lots of discipline and a positive attitude to achieve the goals.

And for discipline, make a timetable according to your day to day activities but not according to your convenience because then you will only think about being convenient and it’s not going to help.

Wake up early, even if you are not an early bird, set your alarm for 1 hour before you wake up, try it for 1 week then decrease 1 hour for the next week. This way you will gradually reach your goal but you will come into practice. 

If you think that everyday you wake up at 9 and suddenly you will start waking up at 4 in the morning then it’s not going to happen. You may be able to do that for 1-2 days but not for long. Start waking up at 7 first then go to 4 gradually.

Plan your day. Whether you go for a run or hit the gym in the morning.

Choose your meals

Not only exercise and waking up early is going to help if after 1 hour of exercise you eat a burger or pizza for lunch.

As it is always said by the experts, losing weight is 80% diet and 20% exercise.

Plan your meals. It is not necessary to eat raw, bland food in the name of diet. You can eat a normal home cooked balanced meal.

Keep in mind that your meal should be a balanced meal containing all the essential nutrients. 


how long does phentermine stay in your system?

Our body is 75% water, so the body needs that amount of water everyday. Even at the very basic level of our existence, the cells need water for their functioning.

If you are on of those poor souls who doesn’t drink much water and is thinking about drinking gallons of water from tomorrow then hold on, it’s not a joke. Like waking up early is a gradual process, drinking a significant amount of water is also a gradual process. Increase your everyday water intake but gradually.

Say no to habits

It’s important to leave your bad habits at bay.

All those cigarettes or weed you smoked and all those glasses of alcohol you have taken and drugs you have consumed are not going to help you in any way.

Just making you lose years from your life and making your life and body unhealthy and ill.


Phentermine is a short acting drug whose effect lasts for 9 – 12 hours but can be found in the body for even 90 days. It is recommended for weight loss but is addictive as well. It should not be consumed without the doctor’s advice.

NOTE: All the information is only for informational purposes and no one should use any drug without proper consultation from the doctor.

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Dr.Komal Sharma

I am currently pursuing my MBBS degree. My journey into the world of poetry commenced during my 12th-grade years, and over the past seven years, I've passionately crafted hundreds of poems while simultaneously delving into various other creative projects. The decision to embark on a career as a medical writer was both instinctual and astute, allowing me to merge my two distinct passions.

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