How Long Phentermine (Adipex) Stays in Your System?

Adipex (Phentermine) is a type of medication that is common as a prescription drug, particularly, for people who are fighting back the issue of obesity.

Its main mechanism to suppress the appetite of the user and The time period is usually three to six weeks for its consumption for obese people, who are also including low-calorie diet and exercise pin their lifestyle.

Phentermine is not only a part of Adipex but it is also present in Lonamin, Fastin, and Zantryl.

Adipex -p (Phentermine)
Adipex-P 37.5 mg Phentermine

These medications are also popular as the most prescribed diet pills on the market.

As their key functionality is quite same to amphetamines and they act as a stimulant.

Therefore, they come under the category of controlled substance.

Learning the answers like

  • What does Phentermine do
  • How does Phentermine work
  • How long does Phentermine stay in your system
  • For How long Adipex stays in your system

Can come handy and help to improve your level of awareness regarding the drug interactions or only possible side effects.

Moreover, phentermine has the tendencies to make you an addict.

What does Phentermine do? or How does Phentermine work?

Phentermine actually acts just like amphetamines in curbing the appetite, it triggers central nervous system, and raise the level of blood pressure.

lose weight fast with phentermine
How phentermine works

It is common to consume phentermine pills or in the form of capsules.

Usually, Phentermine dose and timing depend on the factors like the form you are taking Phentermine weight loss.

  1. How to take Phentermine?
  2. Phentermine half-life
  3. How long does Phentermine stay in your system?
  4. How long Adipex (Phentermine) stays in your system?

Well, as we have mentioned above phentermine pills as well as capsules are available for consumers.

The consumers take one capsule per day in the morning whereas the consumers take phentermine pills half an hour before every meal; it means three times a day.

After a dose, the gastrointestinal tract absorbs this drug and it is on the peak levels in the blood within the duration of 3 to 4.4 hours.

Phentermine half life is around 25 hours; it means this is the time that this drug dose requires by the liver to metabolize it or come out of the body unchanged through the urine.

Moreover, the drug needs around 5 to 6 half-lives to come out of the system completely.

Administration and Dosage

For exogenous obesity:

phentermine dosages
how to take phentermine

There is no hard and fast rule for dose as it depends upon the response rate from the individual user.

Usually, the dose starts with the lowest ratio.

Normally, a usual adult dose is 1 capsule (37.5 mg) per day according to the prescription of a physician.

The user can have this capsule 1 to 2 hours prior or after the breakfast.

However, it is possible to even prescribe some users just the half tablet (18.75 mg) daily if it is what suits them or in some cases,


1 tablet dose into two doses of the half, half tablets (18.75 mg) two times a day, each dose contains just the half tablet.

Learn detailed review on Adipex vs Phentermine.

Phentermine side effects

The following are a few of the side effects

  • Pulmonary hypertension
  • Interference with the ability to engage in hazardous tasks
  • Valvular heart disease

The following adverse reactions are likely to happen with this drug

1. Central nervous system:Restlessness, insomnia, dysphoria, headache, psychosis, overstimulation, dizziness, headache, euphoria, tremor

2. Allergic:Urticaria

3. Endocrine: Abnormal changes in sex drive, impotence

4. Gastrointestinal: Dryness of mouth, diarrhea, constipation, unpleasant taste, other gastrointestinal disturbances

5. Cardiovascular: Regurgitant cardiac valvular disease or primary pulmonary hypertension, raisin in blood pressure, tachycardia, palpitation, ischemic events

Phentermine long-term side effects

Adipex can cause the following side effects for a long time

  • Pulmonary hypertension
  • Constipation
  • Insomnia

Is Phentermine safe?

Drug interactions

1. Monoamine Oxidase Inhibitors

When you use Adipex-P, the use will be contraindicated during or within the period of 14 days following the monoamine oxidase inhibitors administration due to the risk of hypertensive crisis.

2. Adrenergic Neuron Blocking Drugs

Adipex-P is likely to decrease the impact of hypotensive adrenergic neuron blocking drugs.

3. Alcohol

The use of alcohol with Adipex-P is likely to result in a negative drug reaction

4. Insulin and Oral Hypoglycemic Medications

The little tweaks here and there will be necessary for the amount of Insulin and Hypoglycemic medications

Doctor Phentermine prescription pills online
Phentermine precautions

1. Taking simultaneously other drugs for weight reduction

The use of Adipex-P is usually just for a period of a few weeks (monotherapy) for the controlling exogenous obesity.

However, whether or not you can take Adipex-P with other weight reduction related drugs that include prescribed medicines, herbal items, over-the-counter preparations, or serotonergic (agents) like chosen serotonin reuptake inhibitors ( for instance, fluoxetine; fluvoxamine; paroxetine; sertraline), is still uncertain and not part of any study.

Thus, it is better to not co-administer Adipex-P with these drugs.

2. Primary Pulmonary Hypertension

PPH (Primary Pulmonary Hypertension), an uncommon yet frequent fatal disease of the lungs, has been showing up in patients that were using a combination of fenfluramine or dexfenfluramine with Phentermine.

The probability of a connection between PPH and Adipex-P cannot be negligible as there have been several instances where the patients just have taken Phentermine only.

The starting signs of PPH is typically dyspnea whereas other initial signs are likely to include lower extremity edema or syncope, angina pectoris.

Moreover, the patients are encouraged to report instantaneously any deterioration in tolerating exercise.

Immediate discontinuation is necessary for the treatment in patients who show new and bizarre signs of dyspnea, lower extremity edema or syncope, angina pectoris, and the doctors should evaluate the probable presence of pulmonary hypertension.

3. Valvular Heart Disease

The emergence of serious regurgitant cardiac valvular disease, tricuspid or aortic valves; primarily affecting the mitral, has been noticed in healthy individuals who administer Phentermine with dexfenfluramine or fenfluramine for weight loss.

Moreover, the severity of Phentermine role in the etiology of these valvulopathies has not been clear yet and their course once the users restricted these drugs, are still unknown.

4. The drug tolerance

When the body starts developing tolerance to the anorectant impact, the recommended dose should not happen to exceed in the name of improving better results.

It is better to discontinue the drug.

5. Impact on the potential to engage in probably hazardous tasks

Adipex-P is likely to impair the potential of the patient to engage in possibly risky activities like driving a motor vehicle or operating machinery.

Thus, the patient should be cautioned as per the need.

6. Consumption with alcohol

The consumption of alcohol during the period of Adipex-P administration is likely to generate adverse reactions

7. The risk of Abuse and dependence

Adipex-P has the link with amphetamine (d- and dll-amphetamine) pharmacologically as well as chemically and with other linkable stimulant drugs that have been highly abused.

The chances for Adipex-P abuse should be in mind when analyzing the desirability of adding a drug in the form of weight loss program.

Always the minimum possible amount is required to be prescribed at a time to reduce the chances of overdose.

8. Consumption in the patients with hypertension

It is important to be cautious when prescribing Adipex-P for patients with even the slightest hypertension issue.

9. Toxicology (Nonclinical)

Carcinogenesis, impairment of fertility, mutagenesis

Still some studies are required that can confirm the severity of carcinogenesis, mutagenesis or issues of fertility with the use of this drug.

10. The use in the patients on insulin or oral hypoglycemic drugs for Diabetes Mellitus

A decrease in oral hypoglycemic drugs or insulin in patients that are suffering from diabetes mellitus is likely to be required.

Specific scenarios
side effects of phentermine
effects of Phentermine (Adipex-p)

1. Geriatric Utilization

When it is about dose selection for old age people, it is time to be cautious.

It is common to start the dose with the least possible amount, it indicates the frequency of reduced renal, cardiac function or hepatic, and other linkable diseases or other drug therapy.

Additionally, this drug is famous mainly for its excretion through the kidney, and the toxic reactions risk to this drug is likely to be high in patients who have impaired renal function.

The main reason is usually elderly patients have limited renal function.

Therefore, extra care in the dose selection is necessary because it may be useful for evaluating the renal functionality.

2. Renal damage

As per the presence of phentermine in the urine, the exposure increases in the patients who already have renal impairment.

Caution is important when it is about administering Adipex-P for the people with renal impairment.

In the severe cases of renal impairment, reduce the dose of Adipex-P to 15 mg daily.

3. Pediatric Use

Pediatric obesity is usually the result of a chronic condition and this chronic condition demands a long-term treatment whereas Adipex-P can only be used for a short duration.

Thus, due to these conflicting requirements, it is not suggestible for pediatric use. 

4. Lactating Mothers

The transfer of amphetamines into human milk is possible.

However, it is not confirmed in the case of Adipex-P but prevention is better than cure.

Thus, the doctor is the right candidate to decide whether mother needs to go for Adipex-P or better to avoid it after evaluating the importance of this drug for the mother.

5. Pregnancy

The use of Adipex-P during the period of pregnancy cannot bring any potential benefits and it is more likely to end up causing more harms.

It is suggestible for pregnant women to opt for least weight gain and no weight loss even when they are already obese to overweight to start with.

Our Recommendation

Before we talk about our recommended product, let us be clear about one thing; Phentermine is highly toxic and its use is only better when the diseases are caused by it are less severe than those diseases that are caused without or in the absence of its use.

Thus, it is totally a win-win situation to approach for a phentermine online alternative that cannot only generate significant results but also its utilization is safe for human consumption.

We are talking about none other than Phen375.

What is Phen375?

To start with, Phen375 has the support of scientific research on its back and it is mainly due to the fact that it carries an advanced formula for weight reduction.

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It targets improvement in metabolism, elevates energy levels, improved ability to burn fat and curb the cravings for food.

It comes under the category of OTC substances, no prescription at all and its production is done in the USA.

To check things, in more details, you may visit the official website or simply click here to go to a full Phen375 review of this amazing product that is a legitimate alternative to Phentermine.