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Medicines and supplements

Vitamin C and amphetamine salts for ADHD

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Ask your pharmacist or doctor before combining. Two prescribing labels for extended-release mixed amphetamine salts name ascorbic acid, which is vitamin C, as an acidifying agent that lowers amphetamine blood levels. The labels do not say how much vitamin C it takes, so tell your prescriber about any vitamin C you take.1,2

Key facts

  • The extended-release labels give ascorbic acid as an example of an acidifying agent that decreases amphetamine blood levels.1,2
  • The labels' interaction tables list acidifying agents as lowering both the blood levels and the efficacy of amphetamines.1
  • The immediate-release tablet label lists acidifying agents in general and does not name vitamin C.3
  • Most multivitamins contain vitamin C.4

Ask your pharmacist or doctor first

Prescribing labels for extended-release mixed amphetamine salts name ascorbic acid, which is vitamin C, as an example of an acidifying agent that lowers blood levels of amphetamine and can make it less effective. Tell your prescriber if you take vitamin C.1,2

On the medicine's label

What the labels say

The prescribing information for extended-release mixed amphetamine salts has a section on dose changes caused by other drugs. It says agents that change the acidity of urine can change how much amphetamine stays in the blood, and it gives ascorbic acid, the chemical name for vitamin C, as an example of an acidifying agent that decreases blood levels.1,2

A generic extended-release label adds that acidity in the gut matters as well as in urine, and that alkalinizing agents such as sodium bicarbonate do the opposite and raise blood levels.2

Why acidity matters

Part of each dose of amphetamine leaves the body in urine. The label reports that the share cleared this way ranges from 1% to 75% depending on how acidic the urine is, and that drugs which change urine acidity change how fast amphetamine is eliminated.1

Acidifying agents push in the direction of lower blood levels, and the labels say this can make the medicine less effective. That is the reason they are listed among clinically important interactions.1,2

What the labels do not say

The labels do not give an amount of vitamin C at which this starts to matter, and they do not name any food or drink as an acidifying agent. Their instructions are written for prescribers, who judge treatment by how a person responds, so the useful step for you is to tell yours what you take.1

The immediate-release tablet label lists gut and urinary acidifying agents in general without naming vitamin C. That is not evidence either way, so the same advice applies to every form of the medicine.3

Where vitamin C turns up

Vitamin C is in most multivitamins, in single-ingredient supplements, and in some drinks and breakfast cereals that have it added. It may be listed as ascorbic acid or as a mineral ascorbate, such as sodium or calcium ascorbate.4,5

What to ask your pharmacist

  • Does the vitamin C in my supplements matter for my medicine?
  • Does it matter whether my form of the medicine is immediate-release or extended-release?
  • Should I take my supplements at a different time from my medicine?
  • Do my multivitamin, drink mixes or other products contain vitamin C?

Bring the Supplement Facts panel of everything you take, and do not change your medicine dose on your own.

Questions people ask

Can I drink orange juice with amphetamine salts?

The current labels read for this page do not mention fruit juice. They name ascorbic acid as an example of an acidifying agent, so ask your pharmacist about juice as well as supplements.1

Does vitamin C stop the medicine working?

The labels say acidifying agents lower the blood levels and efficacy of amphetamines, but they do not measure the effect for vitamin C. Ask your prescriber rather than changing anything yourself.1

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Sources

  1. Adderall XR (mixed salts of a single-entity amphetamine product) extended-release capsules: prescribing information (Takeda Pharmaceuticals America). DailyMed, U.S. National Library of Medicine. Published May 6, 2026. Opened 2026-10-07.
  2. Dextroamphetamine saccharate, amphetamine aspartate monohydrate, dextroamphetamine sulfate, amphetamine sulfate extended-release capsules: prescribing information (Sun Pharmaceutical Industries). DailyMed, U.S. National Library of Medicine. Published September 28, 2026. Opened 2026-10-07.
  3. Adderall (dextroamphetamine saccharate, amphetamine aspartate, dextroamphetamine sulfate and amphetamine sulfate) tablets: prescribing information (Teva Pharmaceuticals USA). DailyMed, U.S. National Library of Medicine. Published June 18, 2024. Opened 2026-10-07.
  4. Office of Dietary Supplements, National Institutes of Health. Vitamin C: Fact Sheet for Consumers. Updated March 22, 2021. Opened 2026-10-07.
  5. National Institutes of Health, Office of Dietary Supplements. Vitamin C: Fact Sheet for Health Professionals. Updated July 31, 2025. Opened 2026-10-07.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.