Dosing at a Glance
Qsymia uses a fixed-ratio combination design: every capsule contains phentermine and topiramate in a set ratio, not adjusted separately. The four strengths exist so that dose titration proceeds through clean, labeled steps. Compounding, splitting, or off-ratio substitution is not appropriate with this drug.
Unlike many weight-loss drugs that are dosed to response, Qsymia is dosed to a protocol: starter → recommended → (if additional loss is needed) titration → maximum. Skipping the titration is not a shortcut — it causes a sharp spike in side-effect incidence without speeding weight loss.
Complete Dosage Chart
| Strength | Phentermine | Topiramate ER | Label role | Capsule description |
|---|---|---|---|---|
| 3.75 / 23 | 3.75 mg | 23 mg | Starter dose — first 14 days | Purple body, white cap |
| 7.5 / 46 | 7.5 mg | 46 mg | Recommended maintenance dose | Yellow body, white cap |
| 11.25 / 69 | 11.25 mg | 69 mg | Titration step before maximum | Yellow body, yellow cap |
| 15 / 92 | 15 mg | 92 mg | Maximum approved dose | Blue body, yellow cap |
Capsule colors per FDA prescribing information. Actual pill appearance may vary slightly by manufacturing lot.
Titration Schedule
The FDA-approved titration is the same for nearly all adult patients. It is designed around two goals: minimize early side-effect burden (which is what causes most early discontinuations) and build up to a dose high enough to produce clinically meaningful weight loss.
| Week | Dose | What to evaluate |
|---|---|---|
| 1–2 | 3.75 / 23 mg | Tolerance. If severe side effects, discontinue. |
| 3–14 | 7.5 / 46 mg | Weight loss progress. Target: ≥3% of baseline by week 12. |
| 15–16 | 11.25 / 69 mg | Titration step if <3% loss on 7.5/46 at week 12. |
| 17+ | 15 / 92 mg | Maximum. Re-evaluate weight loss at week 12 of this dose. |
The 12-week checkpoint
The FDA label builds in two decision points. The first is at week 12 of the 7.5/46 mg dose:
- Lost ≥3% of baseline weight → continue on 7.5/46 as maintenance.
- Lost <3% of baseline weight → either titrate up to 15/92 or discontinue.
The second checkpoint is at week 12 of the 15/92 mg dose:
- Lost ≥5% of baseline weight → continue on 15/92 as maintenance.
- Lost <5% of baseline weight → discontinue; additional time on Qsymia is unlikely to deliver a meaningful response.
What Is the Highest Dose of Qsymia?
The highest FDA-approved strength of Qsymia is 15 mg phentermine / 92 mg topiramate ER, taken as one capsule once daily in the morning. This is the maximum dose manufactured, the maximum dose studied in the pivotal trials, and the maximum dose legally dispensable in the US. Higher doses of either ingredient separately exist (30 mg phentermine tablets, 200 mg topiramate tablets), but not within the Qsymia brand.
At 15/92, the 56-week trial mean weight loss was about 10.9% of baseline body weight (roughly 22 lb for a 200-lb starting patient). In the SEQUEL 108-week extension, that loss was largely maintained. The trade-off is higher incidence of cognitive side effects, insomnia, and paresthesia compared with 7.5/46.
How to Take Qsymia
- Once daily, in the morning, with or without food.
- Swallow whole — do not split, chew, crush, or open the capsule.
- Take at roughly the same time every day to maintain steady plasma levels.
- Stay hydrated — aim for at least 2 liters of water per day to reduce kidney-stone risk and help with constipation.
- Avoid late-day dosing even if you forget — take tomorrow's dose on schedule instead.
- Avoid alcohol, especially in the first few weeks while you are learning your personal tolerance.
Missed a Dose?
If you realize you missed a dose:
- Before noon → take it as soon as possible and resume normal schedule the next day.
- After noon → skip the dose entirely. Taking Qsymia late in the day will almost certainly cause insomnia that night.
- Multiple missed days (3 or more consecutive) → contact the prescriber. Depending on your dose, re-titration from a lower step may be advised to avoid a resurgence of side effects.
Never take a double dose to "catch up." Fixed-dose combination products have a narrow tolerability window; doubling produces side-effect spikes without improving long-term loss.
Stopping Qsymia Safely
Discontinuation strategy depends on where you are in the titration:
| Current dose | Approach | Reasoning |
|---|---|---|
| 3.75 / 23 | Can stop directly | Topiramate exposure low; seizure-rebound risk minimal |
| 7.5 / 46 | Taper over 1–2 weeks | Drop to 3.75/23 every other day, then stop |
| 11.25 / 69 | Step down to 7.5/46 for 1 week, then 3.75/23 for 1 week, then stop | Moderate topiramate exposure; gradual wean prevents rebound |
| 15 / 92 | Step down to 11.25/69 → 7.5/46 → 3.75/23 → off, 1 week each | Highest topiramate exposure; fastest wean would risk seizure rebound |
Reasons to taper rather than stop abruptly: (1) topiramate is an anticonvulsant, and abrupt discontinuation can lower seizure threshold; (2) many patients experience rebound headache, anxiety, and sleep disturbance on abrupt cessation; (3) appetite rebound is steeper when the stimulant is withdrawn cold.
Special Populations
Renal impairment
In moderate renal impairment (eGFR 30–50 mL/min/1.73 m²), the maximum dose is 7.5/46. In severe renal impairment (eGFR <30), Qsymia has not been adequately studied and is generally avoided. Dialysis patients should not be prescribed Qsymia per current labeling.
Hepatic impairment
In moderate hepatic impairment (Child-Pugh B), the maximum dose is 7.5/46. In severe hepatic impairment (Child-Pugh C), Qsymia is not recommended.
Pediatric (12–17 years)
Qsymia received pediatric approval in 2022 for adolescents 12 and older with obesity (BMI at or above the 95th percentile for age and sex). Dosing follows the same titration schedule as adults, with the same 15/92 maximum, but close monitoring for cognitive and mood effects is advised given adolescent neurodevelopment considerations.
Pregnancy and contraception
Qsymia is contraindicated in pregnancy because of topiramate's association with oral clefts. Patients of reproductive potential must use effective contraception throughout therapy and are required by the REMS to have monthly pregnancy testing. Any confirmed pregnancy is grounds for immediate discontinuation and clinical consultation.
Older adults
No specific dose adjustment based on age alone, but elderly patients are more likely to have renal or hepatic impairment and to be on medications that interact with topiramate (e.g., other CNS depressants, metformin). Start low and go slow.
GLP-1 Dosing Compared
GLP-1s dose differently from Qsymia in three important ways:
- Frequency. Most GLP-1s are weekly subcutaneous injections (semaglutide 2.4 mg, tirzepatide). Orforglipron and oral semaglutide are daily tablets, making them the closest analog to Qsymia's daily-pill format.
- Titration. GLP-1 titration is monthly (start dose → 4 weeks → next dose → 4 weeks → next…) vs Qsymia's week-based schedule. Total time to maintenance is 16–20 weeks, similar to Qsymia's 14 weeks.
- Missed dose rules. For weekly GLP-1s, a missed injection can usually be taken within 5 days of the intended day without changing schedule; for daily oral GLP-1s, skip and resume next day.
Neither class has an inherent dosing advantage. The real divergence is in outcomes per dose step — GLP-1s at maintenance typically deliver more weight loss than Qsymia at maintenance, and in trials, that difference widens at higher doses of the GLP-1 class (e.g., tirzepatide 15 mg).
A Modern Approach Exists
Qsymia was FDA-approved in 2012 — a repurposed stimulant plus an anti-seizure drug. Since then, an entirely new drug class has redefined obesity medicine: GLP-1 receptor agonists. For most patients today, they are more effective and easier to manage.
- 2–3× more weight loss in trials (15–22% vs 7–10% with Qsymia)
- Not a controlled substance — no DEA schedule, no REMS enrollment
- Hormone-based (GLP-1 agonist) — no stimulant, no amphetamine lineage
- Daily oral tablet or once-weekly injection, delivered to your door
- Transparent pricing from $179/month with licensed US providers
- Cancel anytime — no long-term commitment
Licensed US clinicians · HIPAA protected · Medication shipped from US pharmacies
Frequently Asked Questions
What is the highest dose of Qsymia?
The maximum dose of Qsymia is 15 mg phentermine / 92 mg topiramate ER, taken once daily. This is the highest strength manufactured, and it is reached only after a stepped titration: 3.75/23 for 14 days, then 7.5/46 for 12 weeks, then — if additional weight loss is needed — 11.25/69 for 14 days, then 15/92 as the maintenance maximum.
What does Qsymia 15 mg / 92 mg capsule contain?
Each 15/92 capsule contains 15 mg phentermine and 92 mg topiramate extended-release, plus inactive excipients (gelatin, talc, titanium dioxide, iron oxides for capsule coloring, and polymers for the extended-release matrix). The capsule body is purple and the cap is white with orange imprint, per the FDA-approved product description.
How long does it take to titrate up to the maximum Qsymia dose?
About 14 weeks to reach 15/92 mg under the standard protocol: 2 weeks at 3.75/23, then 12 weeks at 7.5/46, 14 days at 11.25/69, and then 15/92 thereafter. The titration exists to minimize side effects — moving faster substantially increases the rate of paresthesia, cognitive slowing, and insomnia.
Can Qsymia be split or crushed?
No. Qsymia capsules should be swallowed whole. Topiramate in Qsymia is formulated as extended release, and crushing or chewing destroys that release mechanism — producing a higher peak concentration, a shorter duration of effect, and amplified side effects. The four available strengths exist precisely so that dose adjustments do not require splitting.
What time of day should I take Qsymia?
Take Qsymia in the morning, ideally before or with breakfast. The phentermine component is a stimulant with a ~20-hour half-life, so evening dosing will almost certainly disrupt sleep. Morning dosing is explicitly recommended in the FDA label. If you miss a morning dose and it is already afternoon, skip it rather than take it late.
What if I miss a dose?
Skip the missed dose and resume your regular schedule the next morning. Do not double up. If you have missed more than three consecutive days, contact your prescriber before restarting at the previous dose — re-titration from a lower strength may be safer to avoid a resurgence of side effects.
Can I stop Qsymia cold turkey?
At the starter dose (3.75/23) and recommended dose (7.5/46), abrupt discontinuation is generally safe. At the higher doses (11.25/69 or 15/92), abrupt discontinuation is not recommended — topiramate withdrawal can precipitate seizures. The standard taper is a step-down over one week for each level of dose before full cessation.
Does Qsymia dose affect weight loss?
Yes, and the relationship is roughly linear across the approved range. At 56 weeks in pivotal trials: 7.5/46 produced about 7.8% placebo-subtracted weight loss; 15/92 produced about 9.8%. The higher dose also produced a higher rate of responders achieving ≥10% loss (48% vs 37%). However, side-effect incidence rises at the higher dose, especially cognitive and mood effects.
Do you need to adjust Qsymia for kidney or liver disease?
Yes for both. In moderate or severe renal impairment (creatinine clearance <50 mL/min), the maximum recommended dose is 7.5/46, not 15/92. In moderate hepatic impairment, the maximum is also 7.5/46. In severe hepatic impairment, Qsymia is not recommended. Dosing in end-stage renal disease and dialysis has not been studied.
- FDA. Qsymia — Prescribing Information. Dosage and Administration section.
- Gadde KM, et al. CONQUER. Lancet. 2011;377:1341–1352.
- Garvey WT, et al. SEQUEL. Am J Clin Nutr. 2012;95(2):297–308.
- Kelly AS, et al. "Phentermine/Topiramate for the Treatment of Adolescent Obesity." NEJM Evidence. 2022;1(6).