Can Vyvanse and Vitamin C Be Taken Together?
Yes, Vyvanse (lisdexamfetamine) and vitamin C can be taken together, but vitamin C should be avoided around the time of Vyvanse administration because it significantly reduces amphetamine absorption and effectiveness.
Understanding the Interaction Mechanism
Vitamin C (ascorbic acid) acidifies the urine, which increases the renal excretion of amphetamines and reduces their therapeutic effect 1. This pharmacokinetic interaction can substantially diminish the clinical efficacy of Vyvanse, potentially leading to inadequate ADHD symptom control despite appropriate dosing 1.
Practical Timing Recommendations
To minimize this interaction while allowing vitamin C supplementation:
- Take Vyvanse in the morning on an empty stomach or with a non-acidic meal 2, 3
- Avoid vitamin C supplements, citrus juices, and high-dose ascorbic acid for at least 1 hour before and 1 hour after taking Vyvanse 1
- If vitamin C supplementation is medically necessary, take it in the evening (at least 8-10 hours after the morning Vyvanse dose) to allow the medication to exert its therapeutic effect throughout the day 2, 4
- Limit dietary sources of high vitamin C (orange juice, grapefruit juice, vitamin C-fortified beverages) around medication administration times 1
Clinical Monitoring
- Monitor for reduced ADHD symptom control if the patient regularly consumes vitamin C-rich foods or supplements near medication times 5, 4
- If breakthrough symptoms occur despite adequate Vyvanse dosing (30-70 mg daily), investigate dietary patterns including vitamin C intake timing 6, 4
- Use standardized ADHD rating scales to objectively assess whether symptom control has changed after dietary modifications 1, 5
Common Pitfalls to Avoid
- Do not assume that small amounts of vitamin C are insignificant—even moderate dietary intake of acidic foods and beverages around medication times can reduce amphetamine bioavailability 1
- Do not discontinue medically necessary vitamin C supplementation without physician guidance, particularly in patients with specific deficiency states; instead, optimize timing 1
- Avoid recommending vitamin C megadoses (>1000 mg daily) in patients taking amphetamine medications, as this substantially increases urinary acidification and drug excretion 1
Special Considerations
For patients requiring both Vyvanse and vitamin C supplementation (such as those with documented deficiency or specific medical conditions requiring supplementation), the evening administration of vitamin C allows therapeutic ADHD coverage during waking hours while maintaining nutritional supplementation 2, 4. Lisdexamfetamine has a duration of action up to 13 hours, so evening vitamin C intake (12+ hours after the morning dose) minimizes interference 7, 4.