It is a well-known rule in the ADHD community that you should never mix Vitamin C with stimulant medication.

However, there is a massive misconception that Vitamin C destroys Vyvanse in the stomach. While that is true for Adderall, Vyvanse works completely differently.

Here is the exact biological mechanism behind how Vitamin C interacts with Vyvanse, why the "stomach acid" myth is wrong, and how you can actually use Vitamin C to dramatically improve your sleep.

The Prodrug Difference

To understand the interaction, you must understand how Vyvanse is absorbed.

Vyvanse is a prodrug (lisdexamfetamine). When you swallow the capsule, it is entirely inactive. It does not matter how acidic your stomach is, because the stomach cannot activate it. The inactive molecule passes through the GI tract, enters the bloodstream, and is eventually cleaved by enzymes in your red blood cells, slowly converting it into active dextroamphetamine.

Because of this prodrug mechanism, drinking orange juice or taking a Vitamin C pill with your morning dose does not block gastrointestinal absorption like it does with Adderall.

So, Can I Take Vitamin C in the Morning?

No. Even though it doesn't block absorption in the gut, taking Vitamin C in the morning will still actively ruin your dose.

Vitamin C (ascorbic acid) must eventually be filtered by your kidneys. When it passes through the kidneys, it drastically acidifies your urinary pH.

The renal clearance rate of dextroamphetamine (the active drug in Vyvanse) is highly dependent on urinary pH. If your urine is acidic, your kidneys treat the active medication in your bloodstream as waste and aggressively flush it into your bladder.

If you take Vitamin C in the morning, your Vyvanse will absorb perfectly fine, but your kidneys will excrete it up to 40% faster. You will experience a massive afternoon crash because the medication was prematurely flushed from your blood.

The 9:00 PM "Vitamin C Flush"

Instead of ruining your morning dose, you can leverage this biological mechanism to solve one of the worst side effects of Vyvanse: Insomnia.

Vyvanse has a very long half-life. Even at 10:00 PM, lingering levels of dextroamphetamine in your bloodstream can prevent your brain from entering deep, restorative sleep.

You can force your body to clear the remaining medication by executing a "Vitamin C Flush."

• The Protocol: Take 1,000mg of Vitamin C exactly 1 to 2 hours before your target bedtime.
• The Result: The ascorbic acid acidifies your urine, signaling your kidneys to rapidly scrub the lingering stimulant out of your blood, allowing your central nervous system to finally power down.

If you are using this protocol, we recommend Performance Lab Vitamin C. It utilizes a nature-identical complex that avoids the heavy gastrointestinal acidity of cheap drugstore ascorbic acid, ensuring it doesn't upset your stomach right before you try to sleep.