Yes, Vyvanse will cause a positive drug screen for amphetamines
Vyvanse (lisdexamfetamine) is a prodrug that metabolizes into d-amphetamine in the body, and therefore will definitively test positive on standard amphetamine drug screens. This is an expected pharmacological result, not a false positive 1.
Why This Occurs
Lisdexamfetamine is enzymatically converted to d-amphetamine after ingestion 2. When drug testing panels screen for amphetamines, they detect amphetamine and its metabolites in urine, which will be present in anyone taking Vyvanse therapeutically.
The critical distinction: This is a "clinical false-positive" for substance abuse, not a true false-positive test result. The drug screen is accurately detecting amphetamine—it simply cannot distinguish between prescribed therapeutic use and illicit drug abuse 3.
Detection Windows
Research demonstrates that amphetamine from lisdexamfetamine can be detected:
- Urine: Up to 77 hours (median) after a single 30 mg dose 4
- Oral fluid: Up to 67 hours (median) after a single dose 4
- Detection times vary significantly between individuals due to pH-dependent excretion 5, 4
Clinical Management Algorithm
When interpreting a positive amphetamine screen in a patient taking Vyvanse:
Obtain complete medication history before ordering or interpreting any drug screen 3
Document the prescription - The positive result is expected and appropriate for patients on prescribed Vyvanse
If confirmation is needed (legal, employment, or custody situations):
- Request confirmatory testing with gas chromatography-mass spectrometry (GC-MS)
- GC-MS will identify the specific amphetamine present (d-amphetamine from Vyvanse) 3
- This can help distinguish prescribed use from illicit methamphetamine or other amphetamines
Consider quantitative levels if monitoring adherence or concerned about misuse - therapeutic levels should correlate with prescribed dosing 3
Critical Pitfalls to Avoid
Never assume a positive amphetamine screen indicates illicit drug use in patients prescribed Vyvanse or other ADHD stimulants 3
Standard immunoassay screens cannot differentiate between prescribed amphetamines (Vyvanse, Adderall) and illicit use - this requires patient history and potentially confirmatory testing 3
Screening cutoffs matter: The standard 1000 ng/mL cutoff may miss low therapeutic doses but will typically detect Vyvanse at prescribed doses 5
pH and hydration affect detection: Alkaline urine and high fluid intake can reduce amphetamine detection, while acidic urine increases excretion and detection 5
Documentation Recommendations
When ordering drug screens on patients taking Vyvanse, document:
- Current prescription and dosage
- Last dose timing
- Purpose of the drug screen
- Label the result appropriately as "consistent with prescribed medication" rather than suggesting illicit use
The FDA label explicitly states that Vyvanse contains lisdexamfetamine, a prodrug of amphetamine, which is a Schedule II controlled substance 1. Any standard amphetamine immunoassay will detect the d-amphetamine metabolite as a positive result.