Phentermine for Weight Loss: Everything You Need to Know - Medical Weight Loss of New York (2024)

September 22, 2022

Medicine, Science

ByWendy Scinta, MD,MS

What is Phentermine?

Phentermine is an FDA approved appetite suppressant pill that has been on the market since 1959. For over 60 years, phentermine has been the most commonly prescribed diet pill in the world.

Phentermine is a sympathomimetic. It is similar in character to the drugs that are used today to treat ADD or ADHD. It works at the level of the hypothalamus to decrease hunger and through its stimulatory effects, increases metabolism.

Because it is similar in structure to stimulants, some patients may experience a “speedy” or “energized” feeling when they first start taking phentermine. This resolves once your body becomes used to the medication, which is typically within the first few weeks of use.

When used correctly, phentermine is safe and inexpensive. When starting phentermine at 37.5mg (the dose used in our office), you should always start with a half pill. It is scored and easily “split-able” by hand or you can use a pill splitter. You may increase the dose to 1 whole pill daily if you begin to feel like the medication is not suppressing your appetite all day.

How is Phentermine Taken?

Phentermine should be taken on an empty stomach so that it can be absorbed properly and work most effectively. It is highly recommended that you take phentermine immediately upon waking so that it does not affect your sleep. You should wait at least 1 hour after taking the medication to eat. Drinking water or black coffee during this 1 hour after taking the medication is fine.

If you eat small breakfasts or no breakfast at all, you may choose to take your pill at 10 or 11 o’clock in the morning when your stomach is not full. Taking it later in the morning is also an option if you fall asleep easily and are a sound sleeper as it will last later in the evening. This tends to prevent evening hunger and cravings.

How Long Can You Take Phentermine?

Provided there are no contraindications or significant side effects, phentermine can be taken as long as necessary to achieve a patient’s treatment goal. It is also an important tool to help maintain weight loss, as it increases metabolism and decreases hunger. Phentermine fights against the body’s natural tendency to push one back to their set point weight.

Side Effects of Phentermine

Most patients who take phentermine will experience a dry mouth. To minimize this sensation, make sure that you drink plenty of water, which for most people should be 60-100 ounces per day.

Some patients will experience mild constipation. Again, keeping your fluid intake high can prevent this. If you are reaching your water goals and still struggling, you can take 2 tablespoons of milk of magnesia morning and night until the constipation subsides. Another option is to use polyethylene glycol powder (Miralax). Dissolve 17g in 8 ounces of water or another beverage daily until the constipation subsides.

All stimulants can potentially raise your blood pressure. If this happens, it is generally mild. If you take medication for high blood pressure, keep a blood pressure journal that has 3 weekly readings. This will help the providers to know how your blood pressure is doing at home and at work. If you don’t own a blood pressure cuff, you can check it at just about any pharmacy. When your weight significantly drops, expect your blood pressure to come down also. This may require taking you off your blood pressure medication.

Who Should Not Take Phentermine?

There are some patients who should not take phentermine. Providers will carefully screen your medical history and list of medications to make sure that you are able to take it.

Do not take this medication if you have:

Severe heart disease
A history of abnormal heart rhythms
Structural abnormalities of the heart
Had a stroke
Peripheral vascular disease
Acute angle closure glaucoma
Seizure disorder
Bipolar disorder

Phentermine is an FDA approved appetite suppressant that helps patients lose weight and maintain that weight loss. This medication must be taken on an empty stomach and you should drink plenty of water daily while taking it. Phentermine is not addicting and can be started and stopped at any time. For additional information, speak to your provider, or call our office at (315) 445-0003.

Tags: Medical Weight Loss, medication, phentermine, Weight Loss Medication, weight management