Phentermine Dosage

Daily Phentermine Dosage Guide

Phentermine is typically prescribed in daily doses ranging from 4mg to 37.5mg worldwide, although some countries permit up to 40mg per day. This medication comes in various forms, including tablets, capsules, and extended-release capsules.

While most patients adhere to one of the standard phentermine doses, the exact instructions for taking phentermine can vary based on individual needs and preferences. Your doctor will provide specific dosing instructions during your initial consultation.

Dose vs. Dosage

It’s important to distinguish between “dose” and “dosage.” A dose refers to the amount of medication taken at one time. At the same time, dosage describes the overall regimen, including the total number of doses and their frequency over a period such as a day.

Choosing the Right Dosage

doctor holding two bottles to decide with gloved hands
A doctor will determine the best phentermine dosage for you

Your doctor will determine the appropriate phentermine dosage for you. Factors influencing this decision include your weight loss goals, age, lifestyle, and any existing medical conditions.

Doctors aim to prescribe the lowest effective dose. However, many patients start with the highest dose, 37.5 mg per day, because phentermine is intended for short-term obesity treatment. The belief is that a higher dose maximizes results quickly.

The choice between tablets and capsules can also affect dosage determination. Tablets are available in 8mg and 37.5mg doses, while capsules come in 15mg, 30mg, and 37.5mg options.

Common Phentermine Dosages

woman looking confusedly at pill
Always take this medication exactly as prescribed.

Here are some typical prescriptions for phentermine:

8 mgAvailable Not available1-3 times per day, 30 minutes before meals
15 mg Not available Available1-2 times per day, 2 hours after eating
18.75 mgAchieved by splitting a 37.5 mg tablet in half Not available1-2 times per day, on an empty stomach
30 mg Not available AvailableOnce per day, before breakfast or 1-2 hours after breakfast
37.5 mg Available AvailableOnce per day, before breakfast or 1-2 hours after breakfast

Detailed Dosage Information

8 mg

lomaira pills

The lowest dose, eight milligrams, is marketed under the brand name Lomaira. This dose is ideal for those who have intense afternoon or evening cravings or who experience side effects with higher doses. Lomaira tablets can also be split to create a smaller dose of 4 mg.

15 mg

The 15 mg dose is suitable for new users, those sensitive to stimulants, or those needing a twice-daily regimen. This dosage often causes fewer side effects while suppressing appetite and boosting energy.

18.75 mg

Phentermine 18.75 mg

This mid-dose is achieved by splitting a 37.5 mg tablet in half. It’s an affordable option for new patients or those tapering off phentermine.

30 mg

Phentermine 30 mg capsules are extended-release and prolong the medication’s effects for 12-14 hours. Some patients achieve this dosage by taking two 15 mg capsules daily.

37.5 mg

Phentermine 37.5 mg is the most commonly prescribed dose due to its effectiveness and convenience. It is the highest dose available in many countries, including the US, Mexico, Argentina, and Chile.

Highest Dose Allowed

The maximum daily dose in the US and South America is 37.5 mg. However, in countries like Australia, New Zealand, and South Africa, doctors can prescribe up to 40 mg using a phentermine-resin-based capsule called Duromine.

If you believe your medication isn’t working correctly, consult your doctor instead of increasing your dose independently. Exceeding the maximum recommended dose can lead to severe side effects or overdose.


white pills spilling out of a white bottle, next to a glass of water
The highest dose of phentermine available in the US is 37.5 mg once per day.

Does a higher phentermine dosage mean faster weight loss?

Not necessarily. While some individuals benefit from a higher dose, others may only experience increased side effects without additional weight loss benefits.

Can you take phentermine twice a day?

Yes, some patients take lower doses twice daily under their doctor’s guidance. For example, two doses of 15 mg each are permissible as they total less than the maximum daily dose of 37.5 mg.

Is 75 mg of phentermine too much?

Taking 75 mg of phentermine in a single day is not safe. This dosage far exceeds the recommended maximum of 37.5 mg per day and can result in severe adverse effects such as dangerously high blood pressure, heart rate irregularities, and even circulatory collapse. In extreme cases, it can be fatal.

What should I do if I miss a dose?

If you miss a dose, take it as soon as you remember unless it’s close to your next scheduled dose or bedtime. Never double up on doses to make up for a missed one.