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Qsymia side effects and how to avoid them

What to expect when taking Qsymia for weight loss
By | Mar. 10, 2025 Medically reviewed by Anne Jacobson, MD, MPH
A prescription bottle with an exclamation mark on it: Qsymia side effects and how to avoid them

Key takeaways

  • Qsymia is used in combination with physical activity and a reduced-calorie diet to support weight loss and weight management in adult and pediatric patients with a high body mass index (BMI) and at least one weight-related medical condition.

  • Qsymia consists of a phentermine and topiramate extended-release formula. Both of these drugs can cause potentially serious side effects.

  • Serious side effects associated with Qsymia treatment include birth defects, suicidal thoughts and actions, eye problems, kidney stones, potentially fatal skin conditions, and more.

  • The most common Qsymia side effects are generally mild, such as dry mouth, constipation, and a tingling sensation in the skin.  

In this article:

Manufactured by Vivus, Qsymia is an oral medication approved by the Food and Drug Administration (FDA) for weight loss in people ages 12 and older. Each extended-release capsule contains a combination of phentermine and topiramate. Phentermine is a Schedule IV controlled substance that acts as an appetite suppressant. Topiramate is normally used as an anti-epileptic and mood stabilizer, but it may also reduce binge eating and fat storage. Qsymia is associated with potentially serious side effects, including birth defects, heart problems, dependency, and more. 

Common side effects of Qsymia

According to clinical research, the most common side effects of Qsymia were constipation, dry mouth, a tingling feeling in the skin, upper respiratory infections, and headaches. 

Other common Qsymia side effects in adults include:

  • Insomnia
  • Dizziness
  • Loss of or changes in taste

Common Qsymia side effects noted in children 12 and older include:

  • Depression
  • Fever
  • Flu-like symptoms
  • Joint pain
  • Sprains
  • Dizziness 

Serious side effects of Qsymia

Serious side effects of Qsymia may include:

  • Birth defects
  • Suicidal thoughts or actions
  • Eye problems, including a sudden loss of vision
  • An eye condition called secondary angle closure glaucoma
  • Kidney stones and other kidney problems, which may present as severe back pain
  • Problems with concentration, memory, and speech
  • Slow growth in children 12 and older
  • Increased acid in the bloodstream (metabolic acidosis)
  • Increased ammonia in the bloodstream
  • Low potassium (hypokalemia)
  • Depression, anxiety, irritability, or other mood changes
  • Trouble sleeping
  • Fever 
  • Decreased sweating in hot weather
  • Serious skin reactions, including a potentially fatal condition marked by rashes and blisters (toxic epidermal necrolysis)
  • Allergic reactions
  • Fragile bones
  • Seizures from stopping Qsymia too fast
  • Increased heart rate

How soon do Qsymia side effects start?

Richa Mittal, MD, says people typically don’t notice Qsymia side effects after a single dose. Instead, expect side effects to crop up after at least a week. “Side effects can often be dose-dependent, so they may not occur on one dose but will occur on another,” she says. 

How long do Qsymia side effects last?

Although some Qsymia side effects can be unsettling at first, they may be temporary. “Some Qsymia side effects, particularly the mild ones like tingling or dry mouth, may lessen or even go away as the body gets used to the medication over time,” says Michael Chichak, MD.   

He recommends talking to your healthcare provider about any side effects that cause significant discomfort or are severe or persistent. Your healthcare provider may adjust the dose of Qsymia or consider alternative weight loss treatments. 

What are the long-term side effects of Qsymia?

Long-term use of Qsymia could increase the risk of some side effects. “Topiramate has been linked with a higher danger of memory problems, attention deficit, and other cognitive defects in the long run,” Dr. Chichak says. He also warns that kidney stones may develop over time as a result of Qsymia, as could a fast heartbeat. 

Another long-term concern is the development of metabolic acidosis, which can increase the risk of kidney disease, osteoporosis, confusion, rapid breathing, and death. In clinical trials, 30% of those who received the maximum dose of Qsymia had metabolic acidosis after one year, compared to just 6% in the placebo group. 

However, Dr. Mittal says Qsymia’s negative impact on the kidneys is rarely permanent, and kidney function should improve after the medicine is discontinued. The same goes for eye pain or vision changes. However, seizures can occur if Qsymia is suddenly stopped, so don’t try to discontinue it without medical guidance. 

Qsymia drug interactions

People who take the following medication should discuss the increased risk of side effects with their healthcare provider before starting Qsymia:

  • Monoamine oxidase inhibitors (MAOIs): Taking Qsymia with MAOIs increases the risk of dangerously high blood pressure.
  • Combined hormonal contraceptives (CHCs): Spotting may occur when using Qsymia alongside birth control pills, vaginal rings, and patches that contain estrogen and progestin.
  • Central nervous system (CNS) depressants: Qsymia may increase the effect of CNS depressants like alcohol, barbiturates, benzodiazepines, and sleep medications, potentially leading to dizziness, poor cognition, and other adverse side effects.
  • Non-potassium-sparing diuretics: Qsymia may increase the risk of low potassium when taken with these medications.
  • Antiepileptic drugs: Taking phenytoin or carbamazepine with Qsymia may decrease the effectiveness of topiramate (one of the active ingredients in Qsymia). In addition, people who take valproic acid with Qsymia may experience an increased risk of hypothermia and high ammonia levels in the blood.
  • Carbonic anhydrase inhibitors: Using Qsymia with acetazolamide (generic Diamox) or similar drugs can increase the risk of kidney stones and metabolic acidosis. 
  • Pioglitazone: Qsymia may decrease the effectiveness of this diabetes medication, causing high blood sugar.
  • Amitriptyline: Qsymia may increase the concentration of amitriptyline in the body, so healthcare providers may prescribe a lower dose of this antidepressant. 

Qsymia and alcohol

Do not drink alcohol while taking Qsymia. Alcohol may interact with the ingredients in Qsymia and cause an increased risk of drowsiness, dizziness, lightheadedness, poor cognition, and poor coordination. Similar risks are associated with using other CNS depressants, such as barbiturates, benzodiazepines, and sleep medications while taking Qsymia.

Safety measures while using Qsymia

Qsymia shouldn’t be taken by people who:

  • Are pregnant or plan to become pregnant
  • Have glaucoma
  • Have an overactive thyroid
  • Have cardiovascular disease
  • Are on dialysis
  • Have a history of suicidality
  • Have a history of substance misuse or dependency
  • Take MAOIs or have taken them in the last 14 days
  • Are allergic to aspirin or FD&C Yellow No. 5 (tartrazine)
  • Are allergic to phentermine or topiramate
  • Are under the age of 12

Qsymia isn’t recommended for people who are breastfeeding because an increased risk of diarrhea and sleepiness has been reported in breastfed infants whose mothers used topiramate, one of the active ingredients in Qsymia. 

In addition, Qsymia may worsen certain conditions, including:

  • Kidney disease
  • Liver problems
  • Epilepsy
  • Metabolic acidosis
  • Depression and other mood disorders
  • Insomnia
  • Glaucoma

Qsymia does not have an FDA black box warning. Tell your healthcare provider about all the medications you take, including vitamins and natural supplements, so they can determine whether Qsymia is safe for you. 

Dependence risk

Phentermine, one of the active ingredients in Qsymia, is a Schedule IV controlled substance with a low risk of chemical dependence and abuse. It’s a sympathomimetic amine like amphetamine and pseudoephedrine, which means it’s capable of stimulating the sympathetic nervous system and potentially causing an adrenaline rush. This makes it a potential target for abuse, but dependence is unlikely when phentermine is used for weight loss under the guidance of a healthcare provider.

People who experience phentermine dependence while using Qsymia may feel depressed and extremely fatigued if the medication is suddenly stopped. 

Topiramate, the other active ingredient in Qsymia, is not known to be habit-forming, but it’s associated with an increased risk of seizures when suddenly stopped. For those who want to stop using Qsymia, a healthcare provider can gradually lower the dose to reduce the risk of withdrawal symptoms and convulsions.

Overdose warning

Death may occur if too much Qsymia is ingested, so it’s crucial to take it exactly as prescribed. Do not take more than 15 mg/92 mg phentermine/topiramate per day. Signs of a Qsymia overdose may include:

  • Aggression
  • Hallucination
  • Restlessness that may be followed by fatigue
  • Panic
  • Confusion
  • Personality changes 
  • Schizophrenia-like symptoms
  • Depression
  • Tremor
  • Rapid breathing
  • Blurred vision or seeing double
  • Dizziness
  • Low or high blood pressure
  • Nausea
  • Vomiting 
  • Diarrhea
  • Abdominal cramps
  • Seizures
  • Coma

A Qsymia overdose requires immediate medical attention. Call 911 or Poison Control (800-222-1222) for emergency medical advice. You may need to induce vomiting or wait for medical personnel to pump the stomach. 

How to avoid Qsymia side effects

  • Avoid pregnancy. Because Qsymia increases the risk of birth defects like cleft palate, people who can become pregnant should use contraceptives and confirm a negative pregnancy test each month. Immediately contact your healthcare provider if you become pregnant while taking Qsymia.
  • Do not stop Qsymia cold turkey. Abruptly discontinuing Qsymia could cause seizures, even in people who have never had a seizure. Set refill reminders to avoid running out of Qsymia. If adverse side effects make it difficult to take Qsymia, contact your healthcare provider for a discontinuation plan instead of stopping the medication all at once.
  • Stay hydrated. Dr. Chichak recommends drinking plenty of water and avoiding caffeinated drinks when taking Qsymia in order to avoid dry mouth, ease tingling sensations in the skin, relieve constipation, and support the kidneys. 
  • Be strategic about timing. People who experience insomnia when taking Qsymia should try to take it first thing in the morning to minimize its effect on sleep. On the other hand, those who experience a depressant effect should consider taking it at night to minimize its effect on daytime energy and concentration.
  • Get routine checkups. Regular blood tests can detect potentially serious side effects—such as low potassium, metabolic acidosis, and even the formation of kidney stones—and allow for an early intervention. But don’t wait for a scheduled visit to communicate concerns with your healthcare provider. “The best way to adjust treatment plans and to ensure overall safety is by being transparent with your physician about new or ongoing side effects,” Dr. Chichak says.
  • Take Qsymia exactly as prescribed. Qsymia is typically prescribed as a once-daily medication. Qsymia doses are gradually adjusted over a period of time, starting with a 3.75 mg/23 mg dose of phentermine/topiramate and potentially increasing to a maximum dose of 15 mg/92 mg. Consider using a calendar to track the exact dose you need to take each day. An alarm can also help you remember to take the medication at the same time each day. Taking Qsymia incorrectly could increase the risk of side effects. 

How to treat side effects of Qsymia

A healthcare provider may recommend slowly discontinuing Qsymia in the event of serious side effects, such as eye problems, kidney problems, or suicidal thoughts and actions. Some side effects, like constipation, insomnia, or depression, may be managed with an adjustment in dose, additional prescription drugs, or over-the-counter medications. Talk to your healthcare provider about any and all side effects to get individualized medical advice.

Bottom line: Is Qsymia safe?

Qsymia is a relatively safe choice for medically assisted weight loss in people 12 years and older who do not have a contraindicated condition like glaucoma, kidney disease, or hyperthyroidism and who do not take a contraindicated medication like an MAOI. Qsymia shouldn’t be taken by people who are pregnant or may become pregnant due to the risk of birth defects, and it’s not recommended for those who are breastfeeding. Qsymia may cause serious side effects but shouldn’t be abruptly discontinued without medical guidance due to the risk of seizures. Healthcare professionals can determine if Qsymia is right for you.