What are the most common Qsymia side effects?

In the CONQUER trial the most commonly reported were dry mouth (about 21% of participants), tingling in the hands and feet (20%), constipation (17%), insomnia (10%), dizziness (9%) and cognitive effects such as difficulty finding words (8%). The FDA label reports similar rates for the full 15/92 mg dose against placebo.

Why does Qsymia need a pregnancy test every month?

The label states that topiramate exposure in the first trimester increases the risk of major congenital malformations, including cleft lip and cleft palate, and of a baby being small for gestational age. It therefore recommends a negative pregnancy test before starting and monthly during treatment for anyone who can become pregnant.

What is the Qsymia REMS programme?

REMS stands for Risk Evaluation and Mitigation Strategy. Because of the risk to a pregnancy, Qsymia is only available through a restricted programme in which only certified pharmacies may dispense it. Your prescriber will explain how to get your prescription filled.

Is the tingling in my hands and feet normal?

Tingling — paraesthesia — is the most distinctive side effect of the topiramate component and was reported by about 1 in 5 participants at the full dose, against 2% on placebo. The label reports that 1% of adults stopped Qsymia because of it. Tell your prescriber if it becomes uncomfortable.

Can I just stop taking Qsymia?

No. The label warns about a risk of seizures if the drug is withdrawn abruptly, and says the 15/92 mg dose should be stepped down gradually rather than stopped in one go. Plan any stop with your prescriber.

Qsymia side effects and warnings

What the FDA label warns about

These come from the Qsymia prescribing information published on DailyMed.

Pregnancy: the most serious warning on the label

The label states that Qsymia can cause fetal harm. Pregnancy registries and epidemiological studies show that a fetus exposed to topiramate in the first trimester has an increased risk of major congenital malformations — including cleft lip and cleft palate — and of being small for gestational age.

Because of that risk, the label recommends a negative pregnancy test before starting Qsymia and monthly during treatment for anyone who can become pregnant. Qsymia is also only available through a restricted REMS programme, which means only certified pharmacies can dispense it.

Other warnings and precautions on the label:

Suicidal behaviour and ideation
Eye problems, including acute myopia and raised pressure in the eye
Mood and sleep disorders
Cognitive impairment
Slowing of linear growth in adolescents
Metabolic acidosis
Decreased kidney function
Risk of seizures if the drug is stopped abruptly
Kidney stones
Reduced sweating and overheating
Low potassium
Serious skin and multi-organ hypersensitivity reactions, including DRESS
Anaphylaxis and angioedema

The label says Qsymia must not be used if you:

Are pregnant
Have glaucoma
Have an overactive thyroid
Are taking a monoamine oxidase inhibitor, or stopped one within the last 14 days
Have had an allergic reaction or idiosyncratic reaction to phentermine, topiramate, sympathomimetic amines, or anything else in the capsule

The label numbers, against placebo

The FDA label reports these adult adverse reaction rates for the full 15/92 mg dose against placebo.

Adverse reaction rates reported on the Phentermine / Topiramate ER FDA label, against placebo
Reaction	Qsymia 15/92 mg	Placebo
Tingling in hands and feet	20%	2%
Dry mouth	19%	3%
Constipation	16%	6%
Dizziness	9%	3%
Change in taste	9%	1%
Insomnia	9%	5%

How many people stopped because of side effects

of adults on Qsymia stopped because of tingling in the hands and feet, and 0.6% because of a change in taste. The label reports discontinuation reason by reason rather than giving a single overall figure for adults.

Rare but serious — when to call your doctor

Call your doctor immediately if you have:

You think you may be pregnant, or you have a positive pregnancy test
New or worsening depression, or any thoughts of harming yourself
Sudden blurred vision, eye pain, or a rapid change in how well you see
Confusion, difficulty concentrating, or trouble finding words
Fast or pounding heartbeat
Severe pain in your side or back, or blood in your urine (possible kidney stone)
A rash, especially with fever, swollen glands, or blistering skin
Reduced sweating with a high body temperature, particularly in hot weather

What actually helps

Strategies that work best, based on trial and community experience.

Drink water consistently

Topiramate raises the risk of kidney stones, and the label lists kidney stones among its warnings. Staying well hydrated is one of the main ways to reduce that risk.

Pregnancy testing on schedule

The label recommends a negative pregnancy test before starting and monthly during treatment for anyone who can become pregnant, along with effective contraception.

Never stop it abruptly

The label warns about seizures on abrupt withdrawal and says the 15/92 mg dose should be stepped down under supervision, not stopped in one go.

Take heat seriously

Reduced sweating and overheating are listed warnings. Be careful in hot weather and during hard exercise, and get help if your temperature rises.

When to push through vs. talk to your doctor

You can push through if...

Mild tingling in your fingers or toes that is not getting worse
Dry mouth that improves with sipping water through the day
Constipation that responds to fluids and fibre
Mild sleep disruption early on

Talk to your doctor if...

Any chance that you are pregnant
New or worsening low mood, or thoughts of self-harm
Blurred vision, eye pain, or a sudden change in your sight
Trouble finding words, confusion or memory problems
Severe pain in your side or back
Any symptom you are unsure about

Common questions

Written and maintained by one person · Built with agentic AI tools · Every number checked against the cited trial · Not medical advice

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Built with agentic AI tools and not a substitute for medical advice

Last reviewed: September 2026

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Medical disclaimer: This website is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any treatment. Prices shown are United States self-pay or list prices and vary by insurance and country.