Can you Take Phentermine Longer than 3 months?

January 9, 2024 |

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This article contains all the information on how long you can take Phentermine and why shouldn’t you use it for more than three months.

Phentermine therapy for weight loss is recommended for three months only because its long-term usage can potentially lead to several severe health issues.  

In the next section, we have included a list of possible risks of taking this pill for a long duration. And if there is another diet pill you could use for a long time without the fear of getting sick?

But first, let’s see why you should limit your phentermine therapy to a few weeks only;

Why can you only take Phentermine for 3 months?

Phentermine is a sympathomimetic agent that influences the central nervous system.

It suppresses the hunger sensation and helps you lose weight by limiting your food intake.

However, phentermine tablets are only prescribed for short-term use as many harmful effects are associated with their long-term dosage.

Actually, when you take Phentermine for a long time, you will see an increased weight loss, but the intensity of its stimulatory impact on the body is also increased.

And as we know, prolonged neural stimulation by the action of drugs is dangerous and imposes the risk of many diseases.

Following are some side effects that may occur due to long-term usage of Phentermine:

1. Pulmonary Hypertension

Phentermine has a tendency to raise blood pressure and heart rate.

Over time, increased pulse rate and BP affect blood vessels’ flexibility and strength and may lead to hypertension.

According to the research, intake of Phentermine for a long time can result in weakness of pulmonary (lungs) blood vessels and pulmonary hypertension.

It also disturbs heart function indirectly as blood supply to the heart from the lungs would exert an additional force on the arterial tissues.

2. Valvular heart disease

Another risk associated with long-term usage of Phentermine is the dysfunction of heart valves. This effect is seen in women with no previous history of cardiac ailments.

When the heart tissues of these patients were examined, a plaque-like encasement was found over the valvular components, which interfered with valve function.

Researchers presume that weight loss medication is the reason for this problem.

3. Stroke

As we discussed earlier, the hypertensive effects of Phentermine weaken blood vessels over time. If the blood vessels are narrow or already weakened, they may completely lose their flexibility and burst.

Such incidents were reported from two women who had mild cerebrovascular problems.

After using Phentermine for many weeks, they were hospitalized with acute symptoms of cerebral stroke.

4. Psychosis

Phentermine’s long-term medication also affects mental well-being along with physical health. Being a psychostimulatory agent, Phentermine can stimulate the secretion of neurotransmitters and stress hormones in the body.

When you constantly have high levels of these neurotoxins and hormones in the blood, your cognitive abilities are damaged, and you may show depressive or anti-social behavior.

A 25-year Korean girl was admitted to a psychiatric ward after using Phentermine.

She had had recurrent episodes of psychosis because she had been using the drug for several months and sometimes took doses higher than recommended.

5. Malnutrition

Using appetite suppressants for very long can lead to malnutrition because many people starve themselves for the sake of calorie intake.

In such cases, there is a chance that you are losing weight due to muscle degeneration instead of burning fats because you have decreased supply of protein in your body.

Hence, if you do not monitor your diet regularly and make conscious efforts to take enough amounts of all necessary dietary ingredients, you may suffer from malnutrition and become weaker.

So, it is necessary for a healthy weight loss that;

  • You take a good amount of proteins to keep your lean muscles intact when you lose weight.
  • Eat fruits and vegetables containing minerals and vitamins vital for proper body functions.
  • Drink plenty of water to save yourself from dehydration and metabolic slump.

Additionally, you can choose a safer diet pill to help you with weight loss instead of worrying about the side effects of stimulatory medicines like Phentermine.

Among over-the-counter appetite suppressants, PhenQ is a good option because it suppresses the urge to binge eat and is also an effective fat burner.

Plus, many people have reported impressive weight loss using this tablet, and some users found it even more effective than Phentermine.

A lady has lost 44 pounds in three months with the help of PhenQ, which shows that it is twice more effective as Phentermine.


How long can you be on Phentermine?

It is recommended to use Phentermine for the short term only (usually for not more than 12 weeks) to avoid adverse effects.

How much weight can you lose on Phentermine in 3 months?

On average, a 3-5% reduction in your initial weight is expected by using Phentermine for three months, but it largely depends on your health condition, body mass index, and lifestyle habits.

Different people have reported losing from 9 Ibs to 20 Ibs after taking Phentermine for three months.

What are the long-term effects of Phentermine on the brain?

Long-term phentermine usage can harden and weaken cerebral blood vessels and may lead to stroke.

And it also affects cognitive functioning, resulting in depression and recurrent psychosis.

What are the long-term effects of Phentermine on metabolism?

It does not affect metabolism in the long term; only mild thermogenic effects are produced for a while after taking the pill.

What is similar to Phentermine over the counter?

PhenQ is a safer, over-the-counter medicine for losing weight.

It suppresses appetite by decreasing the secretion of hunger hormone instead of stimulating stress hormones and also speeds up metabolism to burn fats faster.


Although long-term use of Phentermine and other stimulatory appetite suppressants results in increased weight loss, it is a potentially unsafe practice that can lead to cardiovascular diseases, stroke, and mental issues.

Phentermine is a weight-loss medication that has been proven to be effective for short-term use. Hence, you should use this medicine only for 3 months period.

Even better, you can opt for an over-the-counter diet pill like PhenQ, which is safer and more effective.

Finally, make sure to consult with your doctor to discuss the risks and benefits involved in using weight loss pills and supplements.

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