Vyvanse to Adderall conversion: dosage chart and timing
How 30mg of Vyvanse compares to Adderall XR and IR. The molecular math behind the ~3:1 ratio, onset curves, and what changes during a shortage switch.
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How 30mg of Vyvanse compares to Adderall XR and IR. The molecular math behind the ~3:1 ratio, onset curves, and what changes during a shortage switch.
There is no official FDA conversion table between Vyvanse and Adderall because the two drugs use fundamentally different delivery mechanisms. But clinical pharmacology and prescribing guidelines establish a rough 3:1 to 2.5:1 ratio by milligram weight. A 30 mg dose of Vyvanse provides roughly the same active amphetamine base as 10 mg of Adderall.
This is educational data based on FDA package inserts, peer-reviewed pharmacokinetic studies, and published clinical consensus guidelines. We don't provide medical advice or tell you what to take. Any dosage adjustments or medication switches must be supervised by your prescribing clinician. Read our medical sourcing policy.
Based on 30 mg Vyvanse · Active window: 8–10 hours
Take 10–12.5 mg once daily in the morning with water. Capsules can be swallowed whole or opened and sprinkled onto applesauce.
Active duration is 8–10 hours (vs 10–14h for Vyvanse). Onset is noticeably faster: kicks in within 30–45 minutes compared to Vyvanse's 90–120 minute prodrug delay.
Lisdexamfetamine is an inactive prodrug cleaved into dextroamphetamine (~2.5:1 ratio). A 30 mg Vyvanse capsule delivers ~8.9 mg active amphetamine base, bioequivalent to 10–12.5 mg Adderall XR.
* Medical Notice: Conversions are consensus clinical reference estimates based on published AACAP guidelines and FDA labels. Always confirm dose titration with your prescribing physician.
The molecular math behind the 3:1 ratio
The reason 30 mg of Vyvanse does not equal 30 mg of Adderall comes down to molecular weight.
Vyvanse is lisdexamfetamine dimesylate. It is a molecule of dextroamphetamine bonded to L-lysine. The body must cleave off the lysine amino acid in red blood cells before the dextroamphetamine becomes active. By molecular weight, dextroamphetamine base makes up only 29.5% of lisdexamfetamine dimesylate.
Adderall is a mixture of four amphetamine salts (dextroamphetamine saccharate, amphetamine aspartate monohydrate, dextroamphetamine sulfate, and amphetamine sulfate) containing a 3:1 ratio of dextroamphetamine to levoamphetamine. By weight, pure amphetamine base accounts for roughly 62.6% of mixed amphetamine salts.
Because Adderall contains more than double the active amphetamine base per milligram compared to lisdexamfetamine, 1 mg of Adderall delivers significantly more active stimulant than 1 mg of Vyvanse.
Clinical dosage equivalence chart
In clinical practice, physicians transitioning patients between Vyvanse and Adderall XR (extended-release) or Adderall IR (immediate-release) generally use the following approximate target ranges:
| Vyvanse (Once Daily) | Adderall XR (Once Daily) | Adderall IR (Total Daily / Split Dosing) | Active Amphetamine Base |
|---|---|---|---|
| 10 mg – 20 mg | 5 mg | 5 mg (e.g. 2.5 mg twice daily) | ~3 mg – 6 mg |
| 30 mg | 10 mg | 10 mg (e.g. 5 mg twice daily) | ~8.9 mg |
| 40 mg | 15 mg | 15 mg (e.g. 7.5 mg twice daily) | ~11.8 mg |
| 50 mg | 20 mg | 20 mg (e.g. 10 mg twice daily) | ~14.8 mg |
| 60 mg | 25 mg | 25 mg (e.g. 12.5 mg twice daily) | ~17.7 mg |
| 70 mg | 30 mg | 30 mg (e.g. 15 mg twice daily) | ~20.7 mg |
Prescribers frequently start conservative when switching patients during shortage cycles, stepping down one dosage tier before titrating back up to match symptom control.
Release curves and daily duration
Milligram equivalence only tells you how much active drug enters your bloodstream. It tells you nothing about when it arrives or how abruptly it wears off.
- Vyvanse: Relies on enzymatic cleavage in red blood cells. That rate-limited conversion produces a gradual climb, peaking around hour 3.5. Most clinical trials report therapeutic efficacy lasting 10 to 14 hours. The downward slope is smooth.
- Adderall XR: Uses physical dual-bead coating inside a gelatin capsule. Half the beads dissolve immediately in the stomach; the remaining half dissolve roughly 4 hours later in the small intestine. Blood concentration reaches a bimodal peak around hour 7. That delayed burst frequently causes a midday dip followed by an afternoon drop-off.
- Adderall IR: Dumps the entire dose immediately. Peak blood levels arrive within 2 to 3 hours, and symptom relief lasts 4 to 6 hours. When substituting IR for Vyvanse, patients typically need two or three split doses across the day to avoid repeated crashes.
“Vyvanse felt like a smooth ramp up and a gentle glide down around 5 PM. Adderall XR hits like a double espresso at 8 AM, dips at 1 PM, kicks back in, and then drops off a cliff at 4 PM with cold hands. The mental focus is there, but the physical sensations are night and day.”
The levoamphetamine factor
Vyvanse delivers 100% dextroamphetamine once cleaved. Adderall contains 75% dextroamphetamine and 25% levoamphetamine.
Levoamphetamine triggers stronger peripheral sympathetic nervous system responses: higher resting heart rate, peripheral vasoconstriction, and physical jitters. Dextroamphetamine acts far more selectively on central nervous system dopamine and norepinephrine.
That 25% levoamphetamine component is why patients switching from Vyvanse to Adderall frequently report feeling physically wired even when their mental focus feels identical.
Switching during pharmacy shortages
When generic or brand Vyvanse is out of stock, pharmacies cannot substitute Adderall automatically. Both are Schedule II controlled substances under federal law. Your clinician must issue a completely new electronic prescription.
Call your pharmacy before your clinician transmits the new script. Verifying inventory first prevents days of locked electronic orders between competing chains.
Sources
- DailyMed: Vyvanse (lisdexamfetamine dimesylate) Prescribing Information (FDA Set ID: 704e4378-ca83-445c-8b45-3cfa51c1ecad).
- DailyMed: Adderall XR (mixed salts of a single-entity amphetamine product) Prescribing Information (FDA Set ID: aff45863-ffe1-4d4f-8acf-c7081512a6c0).
- Ermer J, et al. Pharmacokinetic profile of lisdexamfetamine dimesylate in children and adults with ADHD. Clin Pharmacokinet. 2010;49(10):637-646.
- Faraone SV, et al. Comparing the efficacy and safety of lisdexamfetamine and other stimulant formulations for ADHD. J Clin Psychiatry. 2019;80(4):18r12670.
Researched & Written By
Eugene Finch
Lead researcher at TilTaken. Diagnosed with ADHD, investigating software billing structures, FDA Orange Book pharmaceutical patent disclosures, and consumer health pricing transparency without commercial kickbacks.