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Took 2 Phentermine by Mistake: How Would It Go?

Phentermine is a drug used for weight loss and is only available by prescription. A phentermine overdose can have very serious effects, depending on many factors, including its dosage, take-along medication, food, alcohol, or street drugs. A high dose in severe cases can also lead to death.

So, what would happen if you took 2 phentermine by mistake?

It can cause serious side effects if you have taken phentermine twice. The severity of side effects caused by double-dose intake depends on the dosage you are taking. Taking 8 mg of phentermine twice will not lead to chronic side effects. A higher overdose of phentermine can, however, result in serious side effects.

To learn more, keep reading.

Table of Content

What Is Phentermine?

As a sympathomimetic stimulant medication, phentermine is chemically similar to amphetamines. One of the most frequently recommended drugs for weight loss, it is most frequently used to treat obesity.

It works by activating the brain and neural system, raising pulse rate and blood pressure while stifling hunger. A reduced appetite means less calorie intake, which helps control weight.


As part of a diet and exercise plan, it can be used to treat obesity, particularly in those with risk factors such as high blood pressure, high cholesterol, or diabetes. Weight loss can be temporary, and the patient can regain weight after stopping the drug.

How Long Does Phentermine Take to Produce Effects?

When taken orally, phentermine for weight loss can start to work as soon as 30 minutes after administration, and its effects can last anywhere between 4 and 14 hours. When we talk about how long it takes for a person to lose weight. It can also vary depending on the dosage of the drug, the diet, exercise, and the physiological condition of the patient.

Usually, it starts producing its effects after one or three months of use. Generally, this drug is not prescribed for more than 3 months by doctors. It is also important to note that the weight that a patient loses while taking Phentermine can be temporary. If you stop taking this drug, there is a considerable risk of gaining weight again.

Furthermore, Phentermine’s effects gradually diminish over time. If you keep taking this drug, its effectiveness will decrease. Phentermine should be used in conjunction with sustained physical activity and healthy habits to maintain effectiveness and long-term weight loss.

It should only be taken twice or thrice a week. Eat less even if you are not taking Phentermine for the rest of the week. Rather than taking Phentermine, increase your metabolism by increasing your routine to lose weight.

What If You Have Taken Two Doses of Phentermine By Mistake?

One of the most curious questions about phentermine is what happens if you accidentally take two phentermine. An overdose of phentermine can be extremely harmful and depends on several factors, including the dosage and whether the medication is combined with food, alcohol, or other medications.


If you accidentally take two phentermine, go to the hospital right away. Taking 2 Phentermine by mistake can result in severe Phentermine side effects including:

  • Anxiety
  • Tremors (shakiness)
  • Convulsions
  • Rapid breathing
  • Confusion
  • Hallucinations
  • Panic attacks
  • Rhythmic irregularities in the heart (arrhythmias)
  • High blood pressure (hypertension)
  • Low blood pressure (hypotension)
  • Nausea or vomiting
  • Diarrhea 
  • Abdominal cramps
  • Seizures
  • Coma
  • Extreme fatigue

What to Do If You Took 2 Phentermine By Mistake?

It is always difficult to determine the solution to taking an overdose of Phentermine without knowing the dosage of this drug and the medical condition of the patient.

But it is always recommended not to try to sort out this issue by yourself at home without the doctor’s recommendation. 


Taking a double dose of Phentermine or a lower dose like 8 mg cannot actually cause severe side effects in adults. But higher dose double intake can cause more side effects.

Depending on the severity of the overdose, you can:

  • Call your prescribing physician
  • Contact Poison Control Centers online or over the phone (1-800-222-1222)
  • Contact emergency medical services (911)

Call 911 immediately if you or someone with you is already displaying phentermine overdose symptoms, or has trouble breathing, seizing, or collapses

What Is an Overdose of Phentermine?

Depending on the individual, the amount of phentermine required to overdose is different. A patient’s chances of experiencing a phentermine overdose vary depending on their drug interactions, previous exposure to phentermine, biological variables, and lifestyle choices.

The likelihood of overdosing on phentermine is higher in first-time users or those with low tolerance levels. The double intake of active ingredients of Phentermine can create serious issues for these patients. However, seasoned users can also suffer from these side effects. 

If a person is taking some other medications earlier, then overdose can prove more severe.

Consult your doctor and pharmacist before mixing any prescription, medication, or dietary supplement with phentermine. Also while taking phentermine, avoid drinking alcohol, smoking, and consuming too much caffeine.

Can You Die From Taking Phentermine Overdose?

Yes, overdoes of Phentermine can result in death.

This medicine induces a hormonal response similar to “fight or flight” by stimulating the sympathetic nervous system. Small amounts of central nervous system activation can help you lose weight since it reduces hunger and increases energy. However, it is not always beneficial to activate the nervous system more than a limit.

The central nervous system can be overstimulated by phentermine, resulting in dangerously high blood pressure, heart rate, and even circulatory collapse. In addition, phentermine can increase the effects of other medicines if you take too much of them together.

Excess Phentermine consumption can also result in convulsions (seizures) and comas. In the event that too much of this drug is taken, these responses (convulsions) can lead to death from phentermine, especially in people who have other drugs in their systems.

What If You Miss the Phentermine Dose?

If you remember the missed dose much earlier than the time of the second dose, take it. Do not take both doses at the same time or consecutively with short intervals between them. A severe side effect can result otherwise.

An Overview of the Dosage

The dosage of phentermine for an individual depends on his age, medical condition, and tendency to tolerate it. Let’s have a look at the obesity dosage of adults and children when using phentermine for weight loss.

Obesity dosage for adults

  • 8 mg should be taken orally three times a day 30 minutes before meals
  • 15 to 37.5 mg should be taken twice daily, once before breakfast and once afterward
  • It is possible for some patients only to require a dose of 4 mg (one-half tablet) three times a day

Pediatric Obesity Dose (Age 17 years and older)

  • It is recommended to take 8 mg orally three times a day, 30 minutes before meals.
  • Once a day, take 15 to 37.5 mg before breakfast or 1 to 2 hours afterward.


Question: What would happen if I took 2 phentermine pills?

Answer: You should contact your doctor immediately if you accidentally took two phentermine pills. Never try some home remedies to solve this problem. The doctor will recommend strategies for fast elimination of the drug from the body. Additionally, some medicines can be recommended to alleviate its side effects.

Question: Can I take 2 30 mg phentermine?

Answer: It is not recommended to take two doses of 30 mg of Phentermine in a day. It is recommended to take a single dose of 30 mg of Phentermine before breakfast or two hours after breakfast even for adults taking Phentermine to reduce obesity.

Question: What happens if you take too much phentermine?

Answer: Many severe side effects can occur if you take too much Phentermine. It can cause nausea, vomiting, convulsions, abdominal cramps, insomnia, lethargy, hallucinations, tremors, increased heartbeats, hypertension, hypotension, and severe side effects including coma and even death.

Question: Can you take phentermine twice a day?

Answer: As long as you’re taking low doses of Phentermine, it’s okay to take this drug twice a day. It is possible to take phentermine even three times a day if you take 8 mg after each meal. However, it is not recommended to take 30 mg or more of phentermine.


What if you took 2 phentermine by mistake? If you have taken 2 phentermine at a high dose, it can cause severe side effects. Consult your doctor as immediately as you can. Side effects will always be alleviated if the drug is removed quickly from the body. Moreover, taking double dosages does not always cause severe side effects, such as taking 4 mg of phentermine twice at the same time without experiencing any problems.

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