In most parts of the world, phentermine weight loss pills are available in doses ranging from 8mg to 37.5mg. The medication is sold as tablets, capsules and extended-release capsules in a total of six different strengths.
Patients usually take one of the standard phentermine doses, but precise phentermine dosage instructions vary based on individuals needs and preferences.
Dose vs. Dosage
The terms "phentermine dose" and "phentermine dosage" are often used interchangeably. However, it is important to note that dose specifically refers to the amount of medication taken at one time, while dosage describes the prescribed regimen (i.e. total number doses & frequency) over a unit of time, such as one day .
Phentermine dosage varies widely based on a patient's needs, health and preferences, as well as physicians' habits. However, a typical phentermine dosage is :
Some doctors also give modified dosing instructions to better accommodate patients' needs. Splitting phentermine in half is a common way to facilitate alternate doses. Breaking tablets allows patients to easily take a modified dose of 4 mg three times per day, 18.75 mg once per day, or 18.75 mg phentermine twice a day .
Eight milligrams (8 mg) is the lowest-available doseof phentermine. It is not distributed as a generic medication, but instead sold under the brand name Lomaira.
Lomaira is ideal for patients who battle afternoon and evening cravings, or who snack throughout the day, since the frequent doses give patients three separate boosts of phentermine throughout the day . It also proves a promising option for patients who battle strong side effects on higher doses of phentermine. This benefit is augmented by the fact that Lomaira is scored to facilitate easy splitting, which allows patients to take as little as 4 mg of phentermine at a time.
However, not everyone prefers Lomaira. These butterfly-shaped tablets are typically taken three times per day, which is not always convenient - especially for people with busy schedules or irregular mealtimes. More, the low dose of phentermine is not affordable for every patient and some people find the lack of a generic option cost prohibitive.
Phentermine 15mg is the lowest-available dose of generic phentermine. It is ideal for patients that are:
Lower dose pills contain less phentermine HCL per capsule, so they do not produce as strong of a biological response. This means they that they do not suppress appetite or boost energy as strongly as higher-dose options, but it also means that low dose phentermine pills tend to cause fewer side effects.
Phentermine 15 mg is popular among new users because some doctors prefer to start patients on a lower dose and then only increase daily dosage if necessary. It is also ideal for patients that need help losing weight, but react strongly to stimulants and do not need (or tolerate) a higher dose.
Some doctors also prescribe 15mg to patients at the end of their weight loss journey to help minimize the risk of withdrawal symptoms, which sometimes occur after abruptly stopping a higher dose of phentermine.
Low dose phentermine is also prescribed as a twice-a-day prescription in some cases . For people that struggle with afternoon and nighttime snacking, phentermine 37.5 mg sometimes proves ineffective because the medication largely wears off before their most problematic time of day.
In these cases, phentermine 15mg proves an appealing option: taken first thing in the morning and then again midday. Individual dosing schedule varies significantly, so it is important to establish a specific plan with your doctor and then take phentermine exactly as prescribed.
Phentermine 18.75 mg is a mid-dose of phentermine. This dose is not available as an individual unit in the US, but is sold as capsules in other countries. However, many American patients still take phentermine 18.75 mg by splitting phentermine 37.5 mg tablets in half.
Phentermine 18.75 mg has many of the same benefits as Lomaira or phentermine 15mg, plus the added convenience of affordability. Patients can easily purchase generic phentermine 37.5 mg tablets and then split them in half at home to achieve this lower dose of phentermine. As a result, phentermine 18.75 mg is a popular option for new patients, those coming to the end of their treatment (tapering) and individuals who struggle with strong side effects when taking a full dose.
Alternatively, some patients take phentermine 18.75 mg two times per day to help control afternoon and evening snacking. Patients split their 37.5 mg tablet in half and take the first half early in the morning (before breakfast or 1-2 hours after breakfast) and the second half around lunchtime. This dosage schedule helps spread the medication's effects out throughout the day and give patients the appetite suppression and energy boost when they need it most.
Phentermine 30 mg is the second-highest dose of phentermine. It comes as a generic capsuleand should be taken once a day, about two hours after breakfast . This dose is unique because it is sold in an extended-release capsulethat is designed to suppresses appetite for up to 12-14 hours at a time . Some patients also to achieve a daily phentermine dosage of 30 mg by taking two 15 mg capsules per day .
Phentermine dosage should be individualized to patients' specific needs. As a result, physician may start a patient on phentermine 15 mg and then double this dose to phentermine 30 mg if weight loss is not sufficient after the first few weeks (or vice-versa if side effects are too strong).
Likewise, a person that struggles with afternoon and evening cravings may benefit from switching from phentermine 30 mg once a day to phentermine 15 mg twice a day to better control late-night snacking. However, phentermine should not be taken late in the afternoon or evening due to increased risk of stimulant-related insomnia .
Phentermine 37.5 mg is the highest dose of phentermine available in most countries, including the US, Mexico, Argentina and Chile. Due to its effectiveness, affordability and convenience, phentermine 37.5 mg remains the most commonly-prescribed dose of this medication.
Learn everything you need to know about Phentermine 37.5 mg.
The information above provides a detailed discussion of each common dose and dosage of phentermine, but sometimes a quick visual summary is even more helpful. Here is a summary of popular phentermine dosages, including the availability of phentermine tablets and capsules in different doses*:
|8 mg||1-3 times per day, 30 minutes before meals|
|15 mg||1-2 times per day, 2 hours after eating|
|18.75 mg||**||1-2 times per day, on an empty stomach|
|30 mg||Once per day, before breakfast or 1-2 hours after breakfast|
|37.5 mg||Once per day, before breakfast or 1-2 hours after breakfast|
* Based on availability in the USA. ** An 18.75 mg dose can also be achieved in tablet form by splitting a phentermine 37.5 mg tablet in half.
The maximum dose of phentermine per day is 37.5 milligrams in the United States and South America. However, doctors in Australia, New Zealand and South Africa can prescribe Duromine, a phentermine-resin based capsule that comes in doses as high as 40 mg.
Speak with your doctor if you think that phentermine is not working properly. DO NOT increase the dose on your own, and never exceed the phentermine maximum dosage of 37.5 mg per day. Take this medication exactly as prescribed. Do not take it at higher doses or more frequent intervals than prescribed. Do not take phentermine for longer than prescribed .
Taking too much phentermine may worsen adverse side effects and can precipitate a potentially-fatal overdose.
Read more here: phentermine overdose.
While some patients seek the highest dose of phentermine possible, others are more interested in low dose phentermine to help them lose weight. Lomaira, an 8 mg tablet, and phentermine 15 mg capsules are good options for individuals seeking a lower dose of this stimulant medication.
Benefits of low dose phentermine include:
Speak with a doctor if you think that low dose phentermine could help you reach your weight loss goals.
Phentermine dosage is based on weight loss goals, age, lifestyle and existing medical conditions, among other factors.
In general, doctors prescribe the lowest dosage of a medication needed to provide the desired effects. However, it is quite typical for patients to start off with the highest dose of phentermine: 37.5 mg per day. This is because tablets are generally more popular than capsules and Adipex-P, the most popular brand of US phentermine, is only available in this high dose. Also, since phentermine is usually only prescribed for twelve weeks at a time, many doctors and patients find that taking the maximum dose of phentermine per day helps optimize the limited treatment period.
The doctor's or patient's preference for tablets versus capsules may also play into determining phentermine dosage. Tablets are only available in 8mg and 37.5mg doses, while capsules are available in 15mg, 30mg and 37.5mg doses . Duromine, a phentermine resin-based capsule sold in Australia, New Zealand and South Africa, also comes in a 40 mg dose .
Many people think that a higher phentermine dosage will help them to achieve better results and lose weight faster, but unfortunately it is not always that simple.
Due to biological and behavioral differences between patients, a higher dose of phentermine does not always translate into better results. While some individuals benefit from a higher dose, others will only experience an increase in unpleasant side effects. On the flip side, most people enjoy fewer side effects while taking a lower dose of phentermine, but a less potent pill may not provide enough appetite suppression and added energy to successfully achieve lifestyle change in some people. Therefore, it is important to determine appropriate phentermine dosage for weight loss on a case-by-case basis: a balancing act between minimizing side effects and maximizing weight loss.
If you feel that you could benefit from a higher or lower dose of phentermine, speak with your prescribing doctor.
Yes, some patients take low dose phentermine twice a day in accordance with their prescribing physician's instructions. People that struggle with snacking sometimes take phentermine 15 mg twice a day.
This is permissible because 15 mg + 15 mg = 30 mg, which is less than the phentermine maximum dosage of 37.5 mg per day. Likewise, Lomaira (phentermine 8mg) can be taken up to 3 times per day since the total prescription only provides 24 milligrams of phentermine per day.
Instead of prescribing lower dose pills, some doctors ask patients to break phentermine tablets in half. Phentermine 8 mg (Lomaira) and phentermine 37.5 mg (Adipex-P and generic) are both available in tablet form.
Some doctors advise splitting phentermine in half and taking only half a pill, equivalent to 18.75mg, for the first few days. This allows the body to adjust to the medication's effects more gradually, which may help reduce unpleasant side effects like dry mouth and insomnia.
Other doctors suggest splitting phentermine in half and taking one half (18.75mg) before breakfast, and then the second half just before lunch. This spreads the stimulant's effects out throughout the day, which is particularly useful for patients who battle cravings later in the day.
While phentermine tablets can be safely split in half and taken as a divided dose, capsules should not be split, cut or crushed.
No, never take phentermine 37.5 twice a day.
The phentermine maximum dosage is 37.5 milligrams per day, so taking either of these pills twice a day far-exceeds the recommended upper limit for this medication. A daily phentermine dosage of 75 mg is NOT safe. More, extra medication does not improve results and can prove dangerous. At best, taking too much phentermine aggravates unwanted side effects; at worst, taking too much of this stimulant can lead to a potentially-fatal overdose.
If you miss a dose of phentermine, take it as soon as you remember. However, if it is almost time for the next dose (or within 6 hours of your regular bedtime), skip the missed dose and take the next dose at your regular time. NEVER take a double dose of phentermine .
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Dr. Karen Vieira has a Ph.D. in Biomedical Sciences from the University of Florida College Of Medicine. She has worked in hospitals conducting clinical research with patients, as well as in the food industry where she researched food and supplement ingredients for a variety of health conditions.