What are the most common side effects of Qsymia?

The label lists tingling in the hands and feet, dizziness, altered taste, insomnia, constipation, dry mouth among reactions reported in at least 5% of patients. The full frequency table is in the label itself, linked below; any percentage quoted on this page is the label's own figure.

Who should not take it?

The label contraindicates it in these cases: Pregnancy; Glaucoma; Hyperthyroidism; Use with a monoamine oxidase inhibitor, or within 14 days of stopping one; Known hypersensitivity to phentermine, topiramate or any other ingredient of Qsymia, or idiosyncrasy to the sympathomimetic amines. The label notes that anaphylaxis and angioedema have occurred with topiramate.

Do the side effects mean the price is not the issue?

They meet at titration. Most of these reactions are worst in the weeks after a dose increase, and those are also the weeks when some sellers charge a lower starting price. So the months people are most likely to stop are not the months that show what the drug costs. The maintenance price is on the Qsymia price page.

← Qsymia (phentermine/topiramate)

Qsymia (phentermine/topiramate) side effects

Qsymia's FDA label lists 6 common reactions, 16 serious warnings and 5 contraindications. All of them are below in the label's own order; any percentage is the label's own figure, and nothing here is a recommendation.

No clinician has reviewed this page. Label and trial statements are quoted from the FDA label or the trial cited beside them. General guidance is marked as such, and every price carries the date it was verified. That is sourcing, not medical review. What we do and do not check · Who checked the price

Last updated 2026-04-24 — the version of the FDA label this page quotes. Read and dated by Alex Seot.

What are the side effects of Qsymia?

The FDA label for Qsymia lists tingling in the hands and feet, dizziness, altered taste, insomnia and constipation among the reactions reported in at least 5% of patients. The label carries no boxed warning, which is a fact about this label and not a statement that the drug is without risk. The label's serious warnings include fetal harm; suicidal behavior and ideation; eye reactions; and mood and sleep disorders. It is contraindicated in 5 cases, among them pregnancy, meaning the label says not to prescribe it at all. Every line above is quoted from FDA prescribing information for QSYMIA rather than summarized from a secondary source, because a side-effect list paraphrased twice stops being the label. That label version was published 2026-04-24. Frequencies are not repeated here second-hand: the percentage table lives in the label itself, which is linked on the page. This is what the label says, not advice about whether to take it.

Common, and usually manageable

Reactions the label reports in at least 5% of patients.

tingling in the hands and feet
dizziness
altered taste
insomnia
constipation
dry mouth

The label recommends a negative pregnancy test before starting and every month during treatment, and Qsymia is dispensed only through pharmacies certified under an FDA REMS. The top dose must be tapered rather than stopped, because stopping it abruptly can cause a seizure.

Serious, and worth knowing before you start

Fetal harm: topiramate in the first trimester raises the risk of cleft lip or palate and of a baby small for gestational age. The label recommends a negative pregnancy test before starting and monthly during treatment, and the drug is dispensed only through certified pharmacies under an FDA REMS
Suicidal behavior and ideation: antiepileptic drugs including topiramate roughly double the risk. The label says to stop Qsymia if suicidal thoughts appear, and to avoid it after a suicide attempt or with active ideation
Eye reactions: acute myopia with secondary angle-closure glaucoma, and visual field defects. The label says to consider stopping if visual problems occur at any time
Mood and sleep disorders: depression, anxiety and insomnia, with a history of depression raising the risk of recurrence
Cognitive impairment: trouble with concentration, memory and word-finding, more likely with rapid titration or a high starting dose. The label cautions against driving until you know how it affects you, and against alcohol
Slowing of growth in 12- to 17-year-olds: a lower height velocity than placebo over 56 weeks. The label says to monitor height
Metabolic acidosis: the label says to measure electrolytes including serum bicarbonate before starting and during treatment, and to avoid other carbonic anhydrase inhibitors
Decrease in renal function: serum creatinine rises, peaking after 4 to 8 weeks. The label says to measure creatinine before starting and during treatment
Seizures on abrupt withdrawal: the 15 mg/92 mg dose is tapered rather than stopped
Kidney stones: topiramate lowers urinary citrate and raises urine pH. The label says to increase fluid intake and to avoid other carbonic anhydrase inhibitors
Reduced sweating and overheating (oligohidrosis and hyperthermia), mostly reported in children. Watch for it during exercise in hot weather
Low potassium (hypokalemia), worse with non-potassium-sparing diuretics. The label says to measure potassium before and during treatment
DRESS, a multiorgan hypersensitivity reaction with fever, rash and swollen lymph nodes that can be fatal
Serious skin reactions (Stevens-Johnson syndrome and toxic epidermal necrolysis): stop at the first sign of a rash unless it is clearly not drug-related, and do not restart
Anaphylaxis and angioedema, reported after approval
Allergic reactions to the dye FD&C Yellow No. 5 (tartrazine), including bronchial asthma, most often in people with aspirin hypersensitivity

Who cannot take it

Pregnancy
Glaucoma
Hyperthyroidism
Use with a monoamine oxidase inhibitor, or within 14 days of stopping one
Known hypersensitivity to phentermine, topiramate or any other ingredient of Qsymia, or idiosyncrasy to the sympathomimetic amines. The label notes that anaphylaxis and angioedema have occurred with topiramate

Each of these, on its own

What the label says, why it happens, how it tracks the dose schedule and the point at which it stops being ordinary.

What it costs Dosage schedule

Questions

What are the most common side effects of Qsymia?: The label lists tingling in the hands and feet, dizziness, altered taste, insomnia, constipation, dry mouth among reactions reported in at least 5% of patients. The full frequency table is in the label itself, linked below; any percentage quoted on this page is the label's own figure.
Who should not take it?: The label contraindicates it in these cases: Pregnancy; Glaucoma; Hyperthyroidism; Use with a monoamine oxidase inhibitor, or within 14 days of stopping one; Known hypersensitivity to phentermine, topiramate or any other ingredient of Qsymia, or idiosyncrasy to the sympathomimetic amines. The label notes that anaphylaxis and angioedema have occurred with topiramate.
Do the side effects mean the price is not the issue?: They meet at titration. Most of these reactions are worst in the weeks after a dose increase, and those are also the weeks when some sellers charge a lower starting price. So the months people are most likely to stop are not the months that show what the drug costs. The maintenance price is on the Qsymia price page.

Source: FDA prescribing information for QSYMIA, the version published 2026-04-24. Information only, not medical advice: a side effect you are having is a conversation with your prescriber, not with a comparison site.