Red Top Microtainer

A red cap microtainer is a small-volume serum collection tube, mainly for capillary blood sampling when only a little sample is required. Key details: Additive: Either plain (no additive) or Clot activator (varies by manufacturer) Sample type: Serum Volume: ~250–600 μL Mixing: Plain: do not mix With clot activator: invert 5 times Common tests: Biochemistry (LFTs, Urea, Creatinine, Lipids) Serology Hormones Therapeutic drug monitoring Rapid or point-of-care serum tests Typical use cases: Pediatrics & neonates Finger-stick / heel-stick samples Difficult venous access Clinics & outreach programs