Qsymia (phentermine/topiramate) dosage schedule
One capsule each morning. The FDA label below escalates it on a schedule, and the maintenance dose is 7.5 mg / 46 mg daily, reached no earlier than week 3.
| When | Dose | What the label says about it |
|---|---|---|
| Days 1–14 | 3.75 mg / 23 mg | Initiation. |
| Day 15 and on | 7.5 mg / 46 mg | The usual dose. After 12 weeks at this dose (about week 14 of treatment), an adult who has not lost at least 3% of body weight — or a patient aged 12 to 17 whose BMI has not fallen 3% — moves to 11.25/69 for 14 days, then 15/92. |
| Higher steps | 11.25 mg / 69 mg then 15 mg / 92 mg | Only if the response at 7.5 mg/46 mg is insufficient. Moderate or severe kidney impairment (creatinine clearance under 50 mL/min) or moderate liver impairment (Child-Pugh 7 to 9) caps the dose at 7.5 mg/46 mg; mild impairment of either changes nothing. With kidney failure on dialysis, or severe liver impairment (Child-Pugh 10 to 15), the label says to avoid Qsymia altogether. |
Maximum dose: 15 mg / 92 mg daily. The label sets nothing above it.
Does the price change as the dose goes up?
$74.99 a month through Qsymia Engage home delivery at every dose, or $210 for 90 days — $70 a month; Costco members pay $65.99 for a 30-day fill. The cheapest branded route on this site, with a monthly pregnancy test recommended alongside it.
halfrx records Qsymia (phentermine/topiramate) at $75/mo at the maintenance dose, verified 2026-09-22.
What happens if I miss a dose?
If a dose is missed, wait until the next morning and take the usual dose; do not double up. Take it in the morning — the label says to avoid evening dosing because of the possibility of insomnia. The 15 mg/92 mg dose must be tapered, one capsule every other day for at least a week, rather than stopped, to avoid a seizure.
Side effects, from the same label →
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
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Questions
- How long does it take to reach the maintenance dose of Qsymia?
- At the fastest the label allows, week 3. Each step has to be held for its full interval before the next one, and a step can be repeated if the current dose is not tolerated — so the real answer is usually longer than the chart, never shorter.
Every dose and interval on this page is from FDA prescribing information for Qsymia (phentermine/topiramate) , the version published 2026-04-24. Nothing here is a recommendation: the dose you take is the one your prescriber sets, and the schedule is often slowed deliberately for tolerability.