Key takeaways:
Phentermine (Adipex-P, Lomaira) is a weight-loss pill approved for short-term use in people ages 17 and older. For best results, phentermine should be combined with lifestyle changes, including a balanced diet and regular exercise.
The typical phentermine dosage varies based on what form you’re taking. But the total daily amount is usually between 15 mg and 37.5 mg.
Phentermine is a controlled substance, and taking it can lead to misuse and dependence. Be sure to follow your prescriber’s instructions for how to take phentermine safely.
There are ways to save on phentermine, which is available as brand-name and generic medications. With a GoodRx discount, you could save up to 95% off the average retail price of the generic version.
Phentermine is an oral weight-loss pill. It’s also known by the brand names Adipex-P and Lomaira. Phentermine is available as oral tablets, capsules, and orally disintegrating tablets (ODTs), giving you several options to choose from.
Phentermine is a controlled substance, which means it has a risk of misuse and dependence. So it’s best to follow your prescriber’s instructions when taking it.
So, how much phentermine do people usually take for weight loss? The answer can depend on which product and form you’re prescribed. Let’s review the recommended phentermine dosages, including adjustments for kidney problems, what to do if you miss a dose, and more.
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What’s the typical phentermine dosage?
Phentermine is approved for short-term use in people ages 17 and older with a body mass index (BMI) of at least 30. It’s also approved for people with a BMI of at least 27 with one or more weight-related health conditions, such as high blood pressure or diabetes.
The typical phentermine dosage for weight loss usually ranges from 15 mg to 37.5 mg daily. But how much you take and how often you take it depends on the specific product and form you’re prescribed.
Phentermine is available as an oral tablet, capsule, and ODT. You’ll take most forms once daily. It’s best to take your dose in the morning, since taking phentermine in the evening can keep you awake at bedtime.
Lomaira is the exception. You’ll take it 3 times daily before meals. In this case, try to take your last dose early in the evening to avoid trouble falling asleep.
The recommended dosages for each form of phentermine are described in more detail below.
Phentermine tablets
Adipex-P and generic 37.5 mg tablets: The typical dosage of phentermine 37.5 mg tablets is 1 tablet by mouth once daily either before breakfast or 1 to 2 hours after breakfast. This dosage may be adjusted to 18.75 mg (one-half tablet) once or twice daily, based on your individual situation.
Lomaira 8 mg tablets: The typical dosage of Lomaria is 8 mg (1 tablet) by mouth 3 times a day, 30 minutes before meals. Some people may only need 4 mg (one-half tablet) for some or all of their doses.
Phentermine capsules
Adipex-P and generic 37.5 mg capsules: The typical dosage of phentermine 37.5 mg capsules is 1 capsule by mouth once daily either before breakfast or 1 to 2 hours after breakfast.
Phentermine 15 mg and 30 mg capsules: The typical dosage is 15 mg to 30 mg once daily, 2 hours after breakfast.
Phentermine orally disintegrating tablets (ODTs)
Phentermine 15 mg, 30 mg, and 37.5 mg ODTs: The typical dosage of phentermine ODTs is 1 tablet (15 mg to 37.5 mg) dissolved on the tongue once daily in the morning. When taking your dose, make sure your hands are dry before handling the ODT. Place the tablet immediately on top of the tongue so it dissolves. You can then swallow, either with or without water.
Are there any dosage adjustments for medical conditions?
Since it’s a controlled substance, it’s best to take the lowest effective dose of phentermine. And for some people, there are factors that warrant a lower dosage than usual. This includes your age and kidney function.
Older adults
In general, older adults tend to be more sensitive to phentermine. It can lead to dizziness and increase the risk of falls. If you’re age 65 or older, your prescriber may suggest starting with a lower phentermine dosage to minimize its risks.
Kidney problems
Phentermine is removed from the body, in part, by the kidneys. So if you have kidney problems, you may need a lower phentermine dosage. Otherwise, phentermine could build up in your body and increase your risk of side effects.
If you have mild or moderate kidney problems, you may not need a dosage adjustment. But if you have severe kidney problems, your phentermine dosage shouldn’t go higher than 15 mg daily. If you take Lomaira, your prescriber may start with a lower daily dosage and keep an eye on your kidney function. Phentermine isn’t recommended if you have end-stage kidney disease.
What happens if you miss a dose of phentermine?
If you miss a dose of phentermine, take it as soon as you remember. But if it’s close to your next scheduled dose, or if it’s late in the evening, skip the missed dose. Then take your next scheduled dose at the usual time. Don’t take a double or extra dose to make up for a missed dose.
What should you do if you take too much phentermine?
The maximum recommended phentermine dosage is 37.5 mg daily. If you accidentally take an extra dose or two of phentermine, reach out to your healthcare team. This is unlikely to cause serious problems. But you could experience more side effects. With direction from your healthcare team, you can usually address any mild side effects at home.
But taking a large amount of phentermine can lead to an overdose, which is a medical emergency. You may need treatment in a hospital. Symptoms of an overdose can include tremors, confusion, and a rapid heart beat. In serious cases, coma, hallucinations, and even death are possible.
If you or someone you know takes a large amount of phentermine, seek immediate emergency medical care or call Poison Control at 1-800-222-1222 for guidance.
How to save on the cost of phentermine
Phentermine is one of the most commonly prescribed oral weight-loss medications. This is largely due to the fact that it is also one of the most affordable options. GoodRx can help you navigate ways to save on the cost of your phentermine prescription:
Phentermine capsules: The capsules are only available as a generic medication. GoodRx can help you pay as little as $14.54 for a 30-day supply of the 15 mg capsules.
Adipex-P: This is available as both a brand-name and lower-cost generic. You can pay as little as $14.10 for a 30-day supply of the generic 37.5 mg tablets with GoodRx.
Lomaira: Lomaira is only available as a brand-name medication. You can pay as low as $16.62 per month with a free GoodRx discount. If you have commercial insurance, you can pay as little as $0.50 per pill with a copay card from the manufacturer.
Frequently asked questions
Phentermine is FDA approved for short-term use, typically up to 12 weeks. But some research suggests that it may be safe and effective for certain people beyond this timeframe. So your prescriber may have you continue taking phentermine if it’s working for you and side effects aren’t an issue. However, it’s possible to develop tolerance to phentermine. That means it may not work as well for weight loss over time.
Phentermine starts working within a few hours of taking it. Some people notice weight loss within the first 2 weeks of taking phentermine. But for others, it may take 3 months or longer to notice a change in body weight. If you aren’t noticing a difference after taking phentermine for a few months, talk to your prescriber. They may want to increase your dosage or suggest a different weight-loss medication.
You can cut the 37.5 mg phentermine tablet in half and take the half-dose (18.75 mg) twice daily. In this case, you would take it in the morning before breakfast, followed by another half tablet before lunch or in the early afternoon. But you should only do this if your prescriber recommends it. Other forms of phentermine aren’t safe to cut or divide into smaller doses.
The best time to take phentermine is in the morning — either before breakfast or 1 to 2 hours after breakfast. For Lomaira, you should take it 30 minutes before meals, 3 times daily. Avoid taking phentermine in the late evening. Otherwise, you may have trouble sleeping.
Phentermine is FDA approved for short-term use, typically up to 12 weeks. But some research suggests that it may be safe and effective for certain people beyond this timeframe. So your prescriber may have you continue taking phentermine if it’s working for you and side effects aren’t an issue. However, it’s possible to develop tolerance to phentermine. That means it may not work as well for weight loss over time.
Phentermine starts working within a few hours of taking it. Some people notice weight loss within the first 2 weeks of taking phentermine. But for others, it may take 3 months or longer to notice a change in body weight. If you aren’t noticing a difference after taking phentermine for a few months, talk to your prescriber. They may want to increase your dosage or suggest a different weight-loss medication.
You can cut the 37.5 mg phentermine tablet in half and take the half-dose (18.75 mg) twice daily. In this case, you would take it in the morning before breakfast, followed by another half tablet before lunch or in the early afternoon. But you should only do this if your prescriber recommends it. Other forms of phentermine aren’t safe to cut or divide into smaller doses.
The best time to take phentermine is in the morning — either before breakfast or 1 to 2 hours after breakfast. For Lomaira, you should take it 30 minutes before meals, 3 times daily. Avoid taking phentermine in the late evening. Otherwise, you may have trouble sleeping.
The bottom line
Phentermine (Adipex-P, Lomaira) is an oral prescription medication for weight loss. The typical phentermine dosage depends on the form you’re prescribed. But it usually ranges from 15 mg to 37.5 mg per day for people ages 17 and older.
Phentermine is a controlled substance, so it carries a risk of misuse and dependence. Be sure to follow your prescriber’s instructions to safely take phentermine. Reach out to them if you have questions about your dosage or about how to take the medication.
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