Vyvanse and Adderall don’t convert at a 1:1 ratio. Because Vyvanse is a prodrug that must be broken down in the body before it becomes active, it requires a higher milligram dose to deliver the same effect. The most widely used clinical equivalence is that 40 to 50 mg of Vyvanse is roughly equal to 20 mg of Adderall XR.
Why the Milligram Numbers Don’t Match
Vyvanse (lisdexamfetamine) is not active when you swallow it. It has to be converted into dextroamphetamine inside your body first. That conversion happens in red blood cells, where enzymes slowly strip away an amino acid attached to the amphetamine molecule. Only after that step does the drug become the same active ingredient, dextroamphetamine, that does the actual work in your brain.
This extra conversion step means a significant portion of each Vyvanse capsule is essentially packaging, not active drug. A 50 mg Vyvanse capsule ultimately delivers less active amphetamine than 50 mg of a direct amphetamine product like Adderall. That’s why Vyvanse doses are always numerically higher than their Adderall equivalents.
Adderall, by contrast, contains a mix of four amphetamine salts (roughly 75% dextroamphetamine and 25% levoamphetamine) that are already active the moment they’re absorbed. There’s no conversion delay and no “wasted” weight in the pill.
Approximate Dose Equivalence Table
No official FDA conversion chart exists, but the equivalence below is commonly used in clinical practice when switching between the two medications. These are approximate starting points, not exact matches, because individual responses vary.
- Vyvanse 30 mg ≈ Adderall XR 10 mg
- Vyvanse 40 mg ≈ Adderall XR 15–20 mg
- Vyvanse 50 mg ≈ Adderall XR 20 mg
- Vyvanse 60 mg ≈ Adderall XR 25–30 mg
- Vyvanse 70 mg ≈ Adderall XR 30 mg
For Adderall IR (immediate release), which is typically taken two or three times a day, the total daily milligram amount follows the same general ratio. So 20 mg of Adderall IR per day (split into two 10 mg doses) would roughly correspond to 40 to 50 mg of Vyvanse taken once in the morning.
How the Two Medications Feel Different
Even at equivalent doses, the experience isn’t identical. Vyvanse reaches peak blood levels about 4.6 hours after you take it, compared to roughly 3.3 hours for straight dextroamphetamine. That slower ramp-up is by design. It means Vyvanse tends to come on more gradually, with less of a noticeable “kick in” and a smoother arc of focus throughout the day.
Vyvanse also lasts longer. Clinical studies show it improves attention for up to 14 hours in adults and up to 13 hours in children aged 6 to 12. Adderall XR typically covers 10 to 12 hours, and Adderall IR lasts about 4 to 6 hours per dose. So if you’re switching from Vyvanse to Adderall IR, you may need an afternoon dose to maintain the same coverage window.
The other notable difference is that Adderall contains levoamphetamine alongside dextroamphetamine. That levoamphetamine component produces more of a physical, body-level stimulation (increased heart rate, peripheral energy) that some people find helpful and others find jittery. Vyvanse converts only into dextroamphetamine, so its effects lean more toward mental focus with somewhat less physical activation.
Dose Ranges and Ceilings
The FDA-approved dose ranges give useful context for understanding where your dose falls:
- Vyvanse: 30 to 70 mg once daily for ADHD in adults and children 6 and older. The maximum is 70 mg per day.
- Adderall IR: 5 to 40 mg daily, split into up to three doses. The maximum for ADHD is 40 mg per day.
- Adderall XR: 20 mg once daily is the standard adult starting dose, with a maximum of 60 mg per day for adults, 30 mg for children 6 to 12, and 40 mg for teens 13 to 17.
Notice that Vyvanse maxes out at 70 mg while Adderall XR can go up to 60 mg. This might seem close numerically, but because of the prodrug conversion, that 70 mg of Vyvanse delivers less active amphetamine than 60 mg of Adderall XR. If you’re on the maximum Vyvanse dose and switching to Adderall, you won’t need anything close to 70 mg.
What Switching Actually Looks Like
When switching between two amphetamine-based medications, clinicians typically don’t need to do a gradual taper or overlap period. The standard approach, according to The Carlat Psychiatry Report, is to stop one medication and start the other the next day. There’s no cross-taper needed because both drugs work through the same mechanism.
The key is starting on the lower end of the equivalent dose and adjusting from there. If you’ve been taking 50 mg of Vyvanse, your prescriber would likely start you around 20 mg of Adderall XR, then titrate up or down based on how you respond over the following weeks. “Equivalent” doses are population averages. Your metabolism, body weight, and sensitivity to each formulation all influence where you actually land.
One practical thing to keep in mind: if you’re switching from Vyvanse to Adderall IR specifically, your daily routine changes. You go from one morning capsule to two or three pills spread across the day. Some people prefer this because they can fine-tune their afternoon dose. Others find the multiple-dose schedule harder to stick with.
Why Dose Conversions Are Approximate
The conversion between Vyvanse and Adderall will never be a perfect formula because the two drugs differ in more than just potency. Vyvanse’s gradual activation means its effects are spread over a longer window, while Adderall delivers a higher peak concentration over a shorter period. Two people on “equivalent” doses may report very different experiences simply because of how their bodies handle the absorption curve.
The prodrug mechanism also introduces individual variability. The enzyme activity in your red blood cells determines how quickly Vyvanse converts to active dextroamphetamine. If your body converts it efficiently, a given dose of Vyvanse will feel stronger than it would for someone whose conversion is slower. This biological variability is one reason prescribers treat the conversion ratio as a starting estimate rather than a fixed rule.