What is 40 mg of Vyvanse equal to in Adderall? 40 mg of Vyvanse is approximately equal to 12–15 mg of Adderall IR (immediate-release) or 15–20 mg of Adderall XR (extended-release). This equivalence is derived from two independent lines of evidence: the molecular weight calculation showing that lisdexamfetamine contains approximately 29.5% active dextroamphetamine by weight, and direct comparative clinical studies that established a conversion ratio of approximately 2.5:1 to 3:1 (Vyvanse mg : Adderall mg). At this ratio, 40 mg Vyvanse ÷ 2.5 = 16 mg Adderall — which rounds to the 12–15 mg clinical starting estimate, with titration to 15–20 mg based on individual response.
Why the Doses Are Not 1:1: The Molecular Explanation
The most common patient misunderstanding when switching between these medications is assuming a 1:1 milligram equivalence — that 40 mg Vyvanse equals 40 mg Adderall. This is incorrect and can lead to significant underdosing or dangerous overdosing depending on which direction the error is made:
Why Vyvanse requires more milligrams for the same effect:Vyvanse (lisdexamfetamine dimesylate) is a prodrug — the active dextroamphetamine is chemically bonded to L-lysine, which makes up approximately 70.5% of the molecule’s total molecular weight. Only 29.5–30% of Vyvanse’s stated milligram dose represents active dextroamphetamine. The remaining ~70% is pharmacologically inert L-lysine that is cleaved and discarded during enzymatic conversion.
Adderall’s composition:Adderall contains 75% dextroamphetamine and 25% levoamphetamine by active amphetamine composition — all of which is pharmacologically active immediately upon absorption. A 15 mg Adderall tablet delivers 15 mg of combined active amphetamine salts to the bloodstream rapidly.
The result: 40 mg of Vyvanse delivers only approximately 11.8 mg of active dextroamphetamine to the bloodstream. Adderall at 12–15 mg delivers 12–15 mg of combined active amphetamine salts. The equivalence is therefore pharmacologically sound — and a 1:1 interpretation of the milligram numbers would mean a patient switching from 40 mg Vyvanse to 40 mg Adderall would receive more than three times the intended active amphetamine dose.
The Full Conversion Table: Vyvanse to Adderall
All doses below represent approximate starting equivalents based on the combined evidence from molecular weight calculations, comparative clinical studies, and the 2.5:1 to 3:1 clinical conversion ratio:
Vyvanse to Adderall IR (Immediate-Release)
| Vyvanse Dose | Approx. Adderall IR Equivalent | Starting Dose Recommendation |
|---|---|---|
| 20 mg | ~6–8 mg | Start 5 mg IR; titrate by 5 mg |
| 30 mg | ~10–12 mg | Start 10 mg IR; titrate by 5 mg |
| 40 mg | ~12–15 mg | Start 12.5–15 mg IR; titrate by 5 mg |
| 50 mg | ~15–20 mg | Start 15–20 mg IR; titrate by 5 mg |
| 60 mg | ~20–25 mg | Start 20 mg IR; titrate by 5 mg |
| 70 mg | ~25–30 mg | Start 25–30 mg IR; titrate by 5 mg |
Vyvanse to Adderall XR (Extended-Release)
| Vyvanse Dose | Approx. Adderall XR Equivalent | Starting Dose Recommendation |
|---|---|---|
| 20 mg | ~10 mg XR | Start 10 mg XR |
| 30 mg | ~10–15 mg XR | Start 10–15 mg XR |
| 40 mg | ~15–20 mg XR | Start 15–20 mg XR |
| 50 mg | ~20 mg XR | Start 20 mg XR |
| 60 mg | ~20–25 mg XR | Start 20–25 mg XR |
| 70 mg | ~25–30 mg XR | Start 25–30 mg XR |
Adderall to Vyvanse (Reverse Direction)
The reverse conversion — starting from an Adderall dose and finding the Vyvanse equivalent — is the more common clinical scenario when a prescriber is switching a patient from Adderall to Vyvanse:
| Adderall IR Dose | Approx. Vyvanse Equivalent |
|---|---|
| 5 mg | ~10–15 mg Vyvanse |
| 10 mg | ~20 mg Vyvanse |
| 15 mg | ~30 mg Vyvanse |
| 20 mg | ~40–50 mg Vyvanse |
| 25 mg | ~50–60 mg Vyvanse |
| 30 mg | ~70 mg Vyvanse (ceiling) |
| Adderall XR Dose | Approx. Vyvanse Equivalent |
|---|---|
| 10 mg XR | ~20 mg Vyvanse |
| 15 mg XR | ~30 mg Vyvanse |
| 20 mg XR | ~40–50 mg Vyvanse |
| 25 mg XR | ~50–60 mg Vyvanse |
| 30 mg XR | ~50–70 mg Vyvanse |
The Clinical Studies Behind the Conversion
The conversion ratios above are not theoretical — they are grounded in direct comparative clinical data:
Crossover trial 1 — LDX 50 mg vs. MAS-IR 20 mg:A crossover study compared lisdexamfetamine 50 mg with mixed amphetamine salts IR 20 mg as clinically equivalent doses, confirming comparable efficacy profiles at this dose pairing. This establishes a 2.5:1 ratio for this dose range.
Crossover trial 2 — LDX 70 mg vs. MAS-IR 45 mg total daily:Another crossover study used lisdexamfetamine 70 mg versus mixed amphetamine salts IR 15 mg taken three times daily (45 mg total), showing comparable efficacy. This produces a 1.56:1 ratio at the higher end — slightly compressing the conversion at maximum doses.
Paediatric comparative study:A paediatric study directly compared LDX at 30, 50, and 70 mg with MAS-XR at 10, 20, and 30 mg respectively, demonstrating comparable efficacy at these specific dose pairings. This supports a 2:1 to 3:1 conversion ratio across the therapeutic dose range.
Published clinical review (Allen Press, 2009):The Mental Health Clinician peer-reviewed comparison of Adderall XR and Vyvanse confirmed: “MAS XR and LDX are both long-acting stimulants with an approximate duration of action of 10 hours” and noted that the primary differences are in pharmacokinetic profile and formulation architecture rather than pharmacological class. This review forms part of the evidence base for clinical conversion guidance.
The key limitation: No single randomised controlled trial has been specifically designed to establish an authoritative dose conversion table for all Vyvanse-to-Adderall transitions. The conversion ratios represent the best available clinical guidance from available data — not a precisely validated formula. Individual variation in enzymatic conversion efficiency, body weight, and neurobiological response means these ratios should be used as starting points for titration, not as definitive end-points.
What 40 mg Vyvanse Means Clinically
To understand what 40 mg Vyvanse represents in clinical context:
- 40 mg is the second-lowest available Vyvanse dose — above the 20 mg and 30 mg starting doses, well below the 70 mg maximum
- 40 mg Vyvanse delivers approximately 11.8 mg of active dextroamphetamine across a 10–14 hour period
- It is equivalent to approximately 12–15 mg of Adderall IR taken once
- Or approximately 15–20 mg of Adderall XR — which would also provide all-day coverage
- In the paediatric comparative study, Vyvanse 30 mg was compared to Adderall XR 10 mg and Vyvanse 50 mg to Adderall XR 20 mg — interpolating to 40 mg Vyvanse ≈ Adderall XR 15 mg
Where 40 mg Vyvanse sits in the therapeutic range:40 mg Vyvanse is a low-to-moderate dose — appropriate as a second titration step for patients who found 20–30 mg insufficient but have not yet reached the mid-range doses. Many adults ultimately require 50–70 mg for optimal ADHD control.
The Critical Dosing Ceiling Problem
This is the most clinically important implication of the Vyvanse-to-Adderall conversion that patients and prescribers must understand:
The Vyvanse ceiling is 70 mg. At the 2.5:1 conversion ratio, 70 mg Vyvanse is equivalent to approximately 25–30 mg Adderall IR or 25–30 mg Adderall XR.
Many adults previously stable on Adderall XR require doses of 30–40 mg — which exceeds what Vyvanse’s 70 mg ceiling can provide as an equivalent dose:
- Adderall XR 30 mg → Vyvanse equivalent = 50–70 mg (still achievable within ceiling)
- Adderall XR 40 mg → Vyvanse equivalent = ~80–100 mg (above the 70 mg approved ceiling)
- Adderall XR 60 mg total daily → Vyvanse equivalent = ~70 mg daily (at ceiling, likely inadequate for some patients)
The practical implication: Patients who required Adderall XR >30 mg for adequate ADHD control may find that even maximum-dose Vyvanse (70 mg) does not provide equivalent coverage. This is one of the most frequently reported issues in patient communities switching from Adderall to Vyvanse, and it is pharmacologically predicted by the conversion mathematics — not a product quality issue.
The Reddit psychiatry community captures this directly: a clinician notes that “going from Adderall 20mg twice daily to Vyvanse required starting at the maximum dose of 70mg, and many patients feel the switch represents a reduction in total medication”. The TGA conducted a specific investigation into Australian Vyvanse concerns in 2025 and confirmed no quality issues — but the dose ceiling limitation remains real for patients previously on high Adderall doses.
What is 40 mg of Vyvanse equal to in Adderall Hobart
What is 40 mg of Vyvanse equal to in Adderall Devonport
What is 40 mg of Vyvanse equal to in Adderall Launceston
What is 40 mg of Vyvanse equal to in Adderall Tasmania
What is 40 mg of Vyvanse equal to in Adderall Victoria
What is 40 mg of Vyvanse equal to in Adderall Queensland
What is 40 mg of Vyvanse equal to in Adderall Canberra
What is 40 mg of Vyvanse equal to in Adderall Australian Capital Territory
What is 40 mg of Vyvanse equal to in Adderall South Australia
What is 40 mg of Vyvanse equal to in Adderall New South Wales
What is 40 mg of Vyvanse equal to in Adderall Darwin
What is 40 mg of Vyvanse equal to in Adderall Ghan
What is 40 mg of Vyvanse equal to in Adderall Northern Territory
What is 40 mg of Vyvanse equal to in Adderall Australia
What is 40 mg of Vyvanse equal to in Adderall Austria
What is 40 mg of Vyvanse equal to in Adderall Germany
What is 40 mg of Vyvanse equal to in Adderall United Kingdom
What is 40 mg of Vyvanse equal to in Adderall Sweden
What is 40 mg of Vyvanse equal to in Adderall Denmark
What is 40 mg of Vyvanse equal to in Adderall Norway
What is 40 mg of Vyvanse equal to in Adderall Finland
What is 40 mg of Vyvanse equal to in Adderall Iceland
What is 40 mg of Vyvanse equal to in Adderall Netherlands
What is 40 mg of Vyvanse equal to in Adderall Spain
What is 40 mg of Vyvanse equal to in Adderall Ireland
What is 40 mg of Vyvanse equal to in Adderall Switzerland
What Changes When You Switch — Beyond the Dose Number
Even at pharmacologically equivalent doses, switching between 40 mg Vyvanse and its Adderall equivalent involves meaningful experiential differences:
What Stays the Same
- The active pharmacological agent — both ultimately deliver dextroamphetamine to the brain
- The core CNS mechanism — dopamine and norepinephrine reuptake blockade and release
- Side effect class and drug interactions
- ADHD-RS-IV symptom improvement at equivalent doses
What Changes Moving from Adderall to Vyvanse
- Onset: Vyvanse takes 1–2 hours; Adderall IR works in 30–60 minutes
- Duration: Vyvanse lasts 10–14 hours from one dose; Adderall IR lasts 4–6 hours
- Smoothness: Vyvanse has a single gradual arc; Adderall XR has a biphasic profile; Adderall IR has a sharp peak
- Levoamphetamine component: Adderall contains 25% levoamphetamine; Vyvanse delivers only pure dextroamphetamine — patients who valued Adderall’s physical energy component from levoamphetamine may notice its absence
- Flexibility: Adderall IR allows intraday dose adjustment; Vyvanse’s 10–14 hour fixed duration does not
- Abuse deterrence: Vyvanse’s prodrug design prevents non-oral routes of misuse in a way that Adderall does not
What Changes Moving from Vyvanse to Adderall
- Faster onset — more pronounced “coming on” sensation
- More physical stimulant effect — levoamphetamine’s peripheral sympathomimetic contribution
- More re-dosing decisions — Adderall IR requires 2–3 daily doses for equivalent Vyvanse coverage
- More abrupt offset — clearer “wearing off” at the end of each dose window
Safe Switching: The Clinical Protocol
Switching between Vyvanse and Adderall should always be done under prescriber supervision, with the following framework:
When switching from Vyvanse 40 mg to Adderall:
- Use the conversion table as a starting point: begin at 12.5–15 mg Adderall IR or 15 mg Adderall XR
- Do not start at the full calculated equivalent — begin at the lower end of the range (70–75% of the calculated equivalent) and titrate upward
- Monitor response over 3–7 days between dose adjustments
- Titrate in 5 mg increments for Adderall IR or 5–10 mg increments for Adderall XR
- If switching from once-daily Vyvanse 40 mg to Adderall IR, determine whether two-dose daily scheduling (e.g., 10 mg morning + 5 mg afternoon) is needed for equivalent all-day coverage
When switching from Adderall 12–15 mg IR to Vyvanse:
- Start at 30–40 mg Vyvanse as the appropriate equivalent range
- Take Vyvanse in the morning — the delayed onset means the medication must be taken earlier than Adderall to achieve comparable morning timing of therapeutic effect
- Titrate by 10–20 mg increments weekly as needed
Safety and Important Considerations for Australian Patients
- Adderall is not approved or available in Australia — the TGA has not approved mixed amphetamine salts, and Adderall is not PBS-listed. Australian patients familiar with Adderall from overseas travel or prior international residence should discuss transitioning to dexamphetamine IR (the closest Australian equivalent) or Vyvanse with their prescriber
- The Vyvanse-to-dexamphetamine conversion for Australian patients uses the same molecular weight basis: 40 mg Vyvanse ≈ 11.8 mg dexamphetamine — consistent with the Vyvanse-to-Adderall conversion for the dextroamphetamine component
- TGA investigation of Vyvanse 2025: The TGA investigated concerns about Vyvanse’s effectiveness in the Australian market and found no issues of concern — confirming that the medication meets quality and efficacy standards. Patients reporting inadequate response at 40 mg should discuss dose titration with their prescriber rather than interpreting this as a product quality problem
- Both Schedule 8 controlled substances — any dose changes require prescriber authorisation; self-adjusting doses between these medications based on conversion tables is inappropriate and potentially dangerous
Common Misconceptions About the 40 mg Vyvanse / Adderall Conversion
Myth 1: “40 mg Vyvanse = 40 mg Adderall.”This is the most dangerous conversion error. 40 mg Adderall delivers 30 mg dextroamphetamine plus 10 mg levoamphetamine — approximately 3.4 times more active amphetamine than 40 mg Vyvanse provides. A patient who switches from 40 mg Vyvanse to 40 mg Adderall believing them equivalent would receive a dramatically supratherapeutic dose.
Myth 2: “Vyvanse 40 mg is a weak dose that needs to be much higher.”40 mg Vyvanse is a low-to-moderate therapeutic dose — equivalent to approximately 12–15 mg Adderall IR. Whether it is therapeutically sufficient depends on the individual patient’s dose requirement, not the absolute number. Patients accustomed to higher Adderall doses will find 40 mg Vyvanse insufficient — not because it is a “weak” medication, but because it represents a lower equivalent dose than they were previously receiving.
Myth 3: “The conversion ratio is exactly 2.5:1 for all doses.”The comparative clinical studies suggest the conversion ratio varies slightly across the dose range — approximately 2:1 to 3:1 — with the ratio tending toward 3:1 at lower doses and compressing toward 1.5:1 at maximum doses. This is why conversion tables give ranges rather than single equivalents, and why clinical titration after conversion is essential rather than relying on a single calculated number.
Myth 4: “Vyvanse 40 mg and Adderall XR 15 mg will feel exactly the same.”Even at pharmacologically equivalent doses, the experience differs meaningfully — Vyvanse has a delayed 1–2 hour onset versus Adderall XR’s 30–60 minute onset, lacks the levoamphetamine component, and provides 10–14 hours of coverage versus Adderall XR’s 8–10 hours. Two medications can be pharmacokinetically equivalent on paper and still feel noticeably different in daily experience.
FAQ: People Also Ask About 40 mg Vyvanse and Adderall
What is 40 mg Vyvanse equivalent to in Adderall?40 mg Vyvanse is approximately equivalent to 12–15 mg Adderall IR or 15–20 mg Adderall XR. This is derived from a 2.5:1 to 3:1 conversion ratio established by direct comparative clinical studies and supported by molecular weight pharmacokinetic calculations. When switching from Vyvanse 40 mg to Adderall, start at the lower end of this range (12.5 mg IR or 15 mg XR) and titrate based on response over 3–7 days.
How does 40 mg Vyvanse compare to Adderall 30 mg XR?40 mg Vyvanse is substantially less potent than 30 mg Adderall XR. 30 mg Adderall XR is equivalent to approximately 50–70 mg Vyvanse — meaning a patient on Adderall XR 30 mg would need to be at or near the Vyvanse ceiling (70 mg) to achieve equivalent daily amphetamine exposure. At 40 mg Vyvanse, the patient is receiving approximately half the active amphetamine they were on 30 mg Adderall XR.
Is 40 mg Vyvanse a low dose?Yes — 40 mg is at the lower end of the Vyvanse therapeutic range for adults. It is the second-lowest approved dose above the 20–30 mg starting range, with the maximum approved dose being 70 mg. Many adults require 50–70 mg for full therapeutic response. In terms of Adderall equivalence, 40 mg Vyvanse delivers approximately 12–15 mg Adderall IR — a modest amphetamine exposure.
What is 50 mg Vyvanse equivalent to in Adderall?50 mg Vyvanse is equivalent to approximately 15–20 mg Adderall IR or 20 mg Adderall XR. This is directly supported by a crossover trial comparing LDX 50 mg to MAS-IR 20 mg and showing comparable efficacy. The 2.5:1 conversion ratio at this dose gives: 50 mg ÷ 2.5 = 20 mg Adderall — consistent with the clinical study data.
What is 70 mg Vyvanse equivalent to in Adderall?70 mg Vyvanse — the maximum approved dose — is equivalent to approximately 25–30 mg Adderall IR or 25–30 mg Adderall XR. This means patients who previously required Adderall XR doses above 30 mg may not be able to achieve equivalent amphetamine exposure within Vyvanse’s approved dosing ceiling. A patient on Adderall XR 40 mg, for example, would theoretically need approximately 80–100 mg Vyvanse — above the 70 mg maximum.
Why does my 40 mg Vyvanse feel weaker than my previous 20 mg Adderall?This is the most common switching confusion, and the pharmacology explains it. 20 mg Adderall IR delivers 20 mg of active amphetamine salts immediately. 40 mg Vyvanse delivers approximately 11.8 mg of dextroamphetamine gradually over 10–14 hours. The lower total active amphetamine delivery — combined with Vyvanse’s slower onset — means 40 mg Vyvanse will subjectively feel less immediately potent than 20 mg Adderall IR in the first 1–2 hours after dosing. If overall symptom control is inadequate, discuss dose titration with your prescriber.
