ADHD Medication Calculator
Input your ADHD medication and the time you took it. We will estimate your therapeutic window, peak plasma concentration, and the specific hour your comedown will hit.
Important: Pharmacokinetics are highly individualized. This tool provides an estimate based on clinical half-lives. Your genetics, stomach acidity (pH), and diet will alter this timeline. This is not absolute clinical advice.
A prodrug that your body must convert into dexamphetamine. Offers a smoother rise and fall.
Serum Plasma Density Curve
Peak Serum Concentration
The medication reaches maximum density in your bloodstream. You are deep within the "Therapeutic Window" where dopamine levels are saturated and focus is at its highest.
The Comedown Window
The half-life arithmetic is catching up. You may experience irritability, a sudden return of ADHD symptoms, teeth grinding, or a "zombie" feeling.
Rescue Protocol
Safe to Sleep
Blood plasma levels have typically dropped low enough to permit natural melatonin production and deep REM sleep. Note that if you lack magnesium, your nervous system may still feel artificially "wired."
Sleep Protocol
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Want the Complete 30-Day Comedown & Sleep Protocol?
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Typical ADHD Medication Comedown Timeline
Every stimulant prescription follows a predictable plasma decay curve. Knowing when your medication shifts from therapeutic focus into the comedown phase allows you to time your afternoon meals and supplements proactively.
| Medication | Peak Focus Window | Comedown Onset | Full Clearance / Sleep Window |
|---|---|---|---|
| Vyvanse (Extended Release) | Hours 3 to 8 | Hours 9 to 11 | Hours 12 to 14 |
| Adderall XR | Hours 2 to 6 | Hours 7 to 9 | Hours 10 to 12 |
| Adderall IR (Instant Release) | Hours 1 to 3 | Hours 4 to 5 | Hours 6 to 7 |
| Concerta (Methylphenidate XR) | Hours 2 to 7 | Hours 8 to 10 | Hours 11 to 12 |
Why Does the Afternoon Crash Happen?
The afternoon comedown occurs when your circulating medication levels drop below the threshold needed to maintain focus, but remain high enough to stimulate physical adrenaline. During this window, your brain is low on stored dopamine after hours of intense concentration.
This temporary imbalance between low synaptic dopamine and lingering physical stimulation is what causes afternoon irritability, jaw clenching, and emotional fatigue.
3 Simple Steps to Smooth Out Your Comedown
- 1.Eat a protein snack 60 minutes before crash onset: Replenishing amino acids before your medication fully wears off stabilizes blood sugar and provides raw fuel for evening dopamine production.
- 2.Hydrate with electrolytes: Mild dehydration mimics and intensifies comedown fatigue. Drink water with a pinch of salt or electrolyte powder in the early afternoon.
- 3.Take Magnesium Glycinate before bed: Taking 300mg to 400mg of magnesium in the evening relaxes tight jaw muscles and nervous tension so you get deep sleep.
Need a Complete Evening Supplement Plan?
Explore our evidence-backed guides on Best Supplements for Vyvanse and Best Supplements for Adderall to build a routine that protects your focus and sleep.