Key takeaways:
Qsymia (phentermine / topiramate ER) is a combination weight-loss medication. Common Qsymia side effects include numbness and tingling, dry mouth, and constipation. Dizziness, taste changes, and insomnia are also possible.
Qsymia may cause trouble thinking clearly or memory issues for some people. Rarely, it can also cause mood changes and suicidal thoughts.
Qsymia can increase heart rate. Vision problems are also possible. It’s best to contact your care team or seek emergency care for any Qsymia side effects that feel serious or life-threatening.
There are ways to save on Qsymia, which is also available as a lower-cost generic. GoodRx can help you access brand-name Qsymia at an exclusive cash price of $149.10. A manufacturer savings card is also available.
Qsymia is an FDA-approved weight-loss medication. It’s a combination of two medications: phentermine and topiramate.
These two medications work together to reduce food cravings and help you feel full. And unlike some newer weight-loss treatments, Qsymia is an oral pill — no injection required. But that doesn’t mean there aren’t still side effects to consider while you’re taking it.
Qsymia side effects at a glance
Below is an overview of Qsymia side effects reported in clinical trials. Keep in mind that everyone responds differently to medication. So you may develop side effects that aren’t listed here. In that case, reach out to your medical team for guidance.
Common Qsymia side effects:
Numbness and tingling
Dizziness
Taste changes
Insomnia
Constipation
Dry mouth
Cold symptoms
Less common Qsymia side effects:
Attention and memory problems
Joint pain (more common in children)
Increased heart rate
Depression
Anxiety
Suicidal thoughts or behaviors
Slowed growth in children
Vision changes
Kidney problems
Decreased sweating (more common in children)
Skin reactions
In addition to these side effects, there’s also a risk for seizures if you stop taking Qsymia abruptly. For this reason, you shouldn’t stop taking Qsymia on your own. Your prescriber can help you stop taking Qsymia safely if side effects are an issue for you.
Let’s take a closer look at 10 Qsymia side effects and how to manage them.
1. Numbness and tingling
One of the most common Qsymia side effects is numbness or tingling in the hands, feet, or face. While this side effect can be alarming, it's typically not harmful. Numbness and tingling are more common with higher Qsymia doses. But they may get better over time as your body adjusts to the medication.
If numbness or tingling doesn’t go away or gets worse, contact your medical team. They may lower your Qsymia dosage or suggest a different medication.
2. Dry mouth
Dry mouth is another common Qsymia side effect. This is mostly because the phentermine component can decrease how much saliva your mouth makes.
Sipping water regularly throughout the day can help keep your mouth moist. Chewing sugar-free gum or sucking on sugar-free hard candy can also help stimulate saliva production. You can try a saliva substitute as well.
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Dry mouth also makes tooth decay and gum disease more likely. So it’s key to brush and floss regularly and stay on top of your regular dental cleanings.
Let your medical team know if dry mouth is an issue for you. They can make changes to your medication routine, if needed, to help manage it.
3. Constipation
Qsymia can cause constipation for some people. This may also be due to phentermine’s drying effect on the body.
You can often manage mild constipation on your own. First, try increasing the amount of fiber in your diet (fruits, vegetables, and whole grains). It’s also helpful to drink plenty of water to help soften your stool. Regular exercise may also help keep things moving.
If those strategies don’t work, you may want to try an over-the-counter (OTC) stool softener or laxative, such as docusate. But if you’re taking a laxative for more than 7 days, or constipation worsens, let your medical team know. Untreated constipation can lead to more serious problems and shouldn’t go unaddressed.
4. Dizziness
Another common Qsymia side effect is dizziness. Like numbness and tingling, dizziness is more common with higher dosages, and often improves as your body adjusts to taking Qsymia.
It’s best to avoid driving or performing other attention-oriented tasks until you know how Qsymia affects you. Keep in mind that alcohol and other medications, such as first-generation antihistamines, can make dizziness worse. So it’s best to limit your alcohol intake and check with your pharmacist before combining other medications with Qsymia.
If dizziness doesn’t improve or is affecting your daily life, let your care team know. They can help determine the best way to manage it.
5. Taste changes
You may notice a metallic taste or other taste-related changes while you’re taking Qsymia. Taste changes aren’t usually harmful. For some people, it may help them eat less and contribute to weight loss. But for others, it may be bothersome.
If you’re troubled by changes in taste while taking Qsymia, talk to your healthcare team. They may recommend a different weight-loss medication.
6. Insomnia
Insomnia is another potential Qsymia side effect. Phentermine is a stimulant medication, so it may make it harder for you to get a good night’s rest.
It’s recommended you take Qsymia first thing in the morning to help reduce the chance of insomnia. It may also help to have a regular sleep schedule and avoid caffeine or stimulating activities in the evening.
But if these strategies don't help, talk to your healthcare team. They may lower your Qsymia dose or suggest a sleep medication to help.
7. Attention and memory problems
It’s not common, but you may have trouble thinking clearly or focusing while you’re taking Qsymia. You may also have trouble with memory or finding the right word when you’re speaking.
These side effects are slightly more common with higher doses of Qsymia, or if you raise your dose faster than recommended. They’re also more likely if you combine Qsymia with alcohol or other medications with sedative effects, such as some anxiety medications.
As with dizziness, it’s a good idea to avoid driving or other activities that require alertness until you know how Qsymia affects you. And it’s best to avoid or limit alcohol while you’re taking Qsymia.
Let your prescriber know if you experience any thinking-related side effects. They’ll likely need to lower your Qsymia dosage or switch you to another medication.
8. Increased heart rate
Some people experience an increased heart rate while taking Qsymia. This is related to phentermine’s stimulant effects.
It can be alarming to feel your heart beating faster than usual. But in most cases, this side effect isn’t serious and should go away as your body adjusts to the medication. However, if you have a history of heart problems, Qsymia may not be the best medication for you.
Your prescriber will likely keep an eye on your heart rate while you’re taking Qsymia. But let them know if you notice a fast heartbeat for long periods of time — especially when you’re resting. They may need to lower your Qsymia dosage.
If you have chest pain or trouble breathing along with a fast heart rate, seek emergency care. These could be signs of a more serious issue.
9. Suicidal thoughts
Topiramate, one of the medications in Qsymia, has been linked to an increased risk of suicidal thoughts. All anti-seizure medications require a warning about this side effect. It can happen as early as 1 week after starting Qsymia, but can also appear at any time during treatment.
Let your healthcare team know right away if you or your child experience any changes in mood or behavior while taking Qsymia.
If you or someone you know is having thoughts of suicide, you’re not alone, and help is available. Call the 988 Suicide & Crisis Lifeline at 988, or text HOME to 741-741 to reach the Crisis Text Line.
10. Vision changes
In rare cases, Qsymia may cause vision changes or eye pain while you’re taking it. Most of the time, these will resolve once you stop taking Qsymia. But in some cases, vision changes are related to a more serious increase in the pressure inside your eye.
Increased eye pressure typically happens within the first month of starting Qsymia. Symptoms include sudden eye pain and blurred vision.
If you notice any vision changes or eye pain while taking Qsymia, it’s best to seek emergency care right away. Prompt treatment can help prevent long-term vision issues. You’ll likely need to stop taking Qsymia if these symptoms occur.
How to save on Qsymia
There are ways to save on Qsymia, which is available as a brand-name medication as well as a lower-cost generic. GoodRx can help you navigate ways to save money on your prescription.
Save with GoodRx: Anyone with a valid prescription, regardless of insurance status, can use GoodRx to purchase a 30-day supply of brand-name Qsymia at an exclusive cash price of $149.10. And you can pay as little as $59.05 for a 30-day supply of the generic with a free GoodRx discount.
Save with a copay savings card: If you have commercial insurance, you may be eligible to pay as little as $70 for brand-name Qsymia using a savings card from the manufacturer. A home-delivery program called Qsymia Engage is also available.
Frequently asked questions
In studies, most people experienced significant weight loss within the first 8 weeks of taking Qsymia. But if you haven’t lost at least 3% of your starting body weight after 12 weeks of treatment, your prescriber may increase your dosage to see if that works better for you. Keep in mind that Qsymia works best when you combine it with a reduced calorie diet and consistent exercise. Talk to your prescriber if you have concerns about whether Qsymia is an effective treatment option for you.
Qsymia isn’t recommended for those living with hyperthyroidism (an overactive thyroid) or severe liver or kidney problems. You also shouldn’t take Qsymia if you’re pregnant or trying to become pregnant, as it carries a risk for severe birth defects. Talk to your prescriber about whether Qsymia is a safe option for you if you have a history of heart disease, glaucoma, or currently take an antidepressant medication. A different weight-loss medication may be a safer option for you.
Yes, Qsymia may cause anxiety or agitation for some people. In some cases, this is due to phentermine’s stimulant effects. In this case, it typically improves as your body adjusts to the medication. But the topiramate component of Qsymia can also cause more long-lasting mood changes for some people. If you notice feelings of anxiety or other mood changes that aren’t improving while taking Qsymia, let your prescriber know. A different weight-loss medication may be a better option for you.
In studies, most people experienced significant weight loss within the first 8 weeks of taking Qsymia. But if you haven’t lost at least 3% of your starting body weight after 12 weeks of treatment, your prescriber may increase your dosage to see if that works better for you. Keep in mind that Qsymia works best when you combine it with a reduced calorie diet and consistent exercise. Talk to your prescriber if you have concerns about whether Qsymia is an effective treatment option for you.
Qsymia isn’t recommended for those living with hyperthyroidism (an overactive thyroid) or severe liver or kidney problems. You also shouldn’t take Qsymia if you’re pregnant or trying to become pregnant, as it carries a risk for severe birth defects. Talk to your prescriber about whether Qsymia is a safe option for you if you have a history of heart disease, glaucoma, or currently take an antidepressant medication. A different weight-loss medication may be a safer option for you.
Yes, Qsymia may cause anxiety or agitation for some people. In some cases, this is due to phentermine’s stimulant effects. In this case, it typically improves as your body adjusts to the medication. But the topiramate component of Qsymia can also cause more long-lasting mood changes for some people. If you notice feelings of anxiety or other mood changes that aren’t improving while taking Qsymia, let your prescriber know. A different weight-loss medication may be a better option for you.
The bottom line
Qsymia (phentermine / topiramate ER) is a combination weight-loss medication. Common Qsymia side effects include numbness or tingling, dry mouth, and constipation. Dizziness, taste changes, and trouble sleeping are also possible.
You may have trouble thinking clearly or notice a faster heart rate than usual while you’re taking Qsymia. In most cases, these side effects should resolve on their own. But be sure to let your medical team know if they worsen or don’t go away.
More serious Qsymia side effects include vision problems and suicidal thoughts or behaviors. It’s best to contact your healthcare team right away if they appear. And don’t hesitate to seek emergency care for any Qsymia side effects that feel serious or life-threatening.
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References
Hesdorffer, D. C., et al. (2009). The FDA alert on suicidality and antiepileptic drugs: Fire or false alarm? Epilepsia.
Johnson, D. B., et al. (2023). Topiramate and phentermine. StatPearls.
MedlinePlus. (2023). Phentermine and topiramate.
National Institute of Dental and Craniofacial research. (2024). Dry mouth.
Qsymia. (n.d.). Savings offers.
Vivus LLC. (2023). Qsymia- phentermine and topiramate capsule, extended release [package insert].
