Educational Content: This article is for informational purposes only and does not constitute medical advice. Always consult a healthcare provider for diagnosis and treatment.
Definition of Litmus
Medically reviewed by Min Clinic Staff | Updated: January 2026
Litmus: A pigment used as a test for acidity and alkalinity. Litmus paper turns red in acid and blue in an alkaline solution. Litmus is prepared from lichens like Roccella tinctoria. Figuratively, a litmus test is a decision in which a single factor is the determinant.