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.
August 18, 2026 · 4 min read · Prices re-checked August 18, 2026
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.
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 the system. It tells you nothing about when it arrives or how long it stays.
Vyvanse relies on enzymatic cleavage in your bloodstream, producing a gradual climb with a peak (Tmax) around 3.5 hours post-dose. Most clinical trials report efficacy lasting 10 to 14 hours, though many patients experience a taper around hour 8 to 10.
Adderall XR uses a physical bead delivery system inside a gelatin capsule. Half the beads dissolve immediately in the stomach, while the other half dissolve roughly 4 hours later in the small intestine. Peak plasma levels arrive around 7 hours post-dose. Because the second pulse drops in mid-afternoon, some patients report a noticeable dip or sharper afternoon crash compared to Vyvanse.
Adderall IR releases all medication at once. Peak blood concentration hits within 2 to 3 hours, and therapeutic benefit lasts 4 to 6 hours. When substituting IR for Vyvanse, patients generally require two or three doses spaced across the day to maintain steady focus.
The levoamphetamine factor
Vyvanse delivers 100% dextroamphetamine once cleaved. Adderall contains 75% dextroamphetamine and 25% levoamphetamine.
Levoamphetamine has stronger peripheral sympathetic nervous system effects (increased heart rate, peripheral vasoconstriction, physical wakefulness) compared to dextroamphetamine, which acts more selectively on central nervous system dopamine and norepinephrine.
Some people switching from Vyvanse to Adderall report feeling more physical restlessness or jitteriness at equivalent doses because of that 25% levoamphetamine component.
Switching during pharmacy shortages
When generic Vyvanse or brand Vyvanse is out of stock, pharmacists cannot automatically substitute Adderall. Because both are Schedule II controlled substances under US federal law, your doctor must write a brand-new prescription with explicit dosage instructions.
Check local pharmacy inventory before your provider sends the new electronic script. Calling ahead saves days of delayed transfers between competing retail 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.