The Dengue NS1 Antigen Blood Test is a blood test used for the early detection of dengue virus infection. It detects the NS1 (Non-Structural Protein 1) antigen, which is released into the bloodstream during dengue infection. Best time for testing: Usually during the first 1–7 days of fever. This test is commonly used in patients with symptoms such as fever, headache, body aches, nausea, rash, or pain behind the eyes, especially in areas where dengue is prevalent.