- RAS (KRAS and NRAS, all RAS) testing
- RAST test
- RBC Acetylcholinesterase
- RBC count
- RBC folate
- RF
- RPR
- RSV (Respiratory Syncytial Virus)
- Rapid diagnostic test (RDT)
- Rapid flu test
- Rapid urease test (RUT) for H. pylori
- Real-time CGM (rtCGM)
- Red Blood Cell (RBC) Antibody Identification
- Red Blood Cell (RBC) Antibody Screen
- Red Blood Cell Count
- Red Cell Indices
- Red blood cell morphology
- Red cell Acetylcholinesterase
- Renal Function Panel/tests
- Renal Panel
- Renal Stone Analysis
- Renal Stone Risk Panel
- Renal function tests
- Respiratory Culture
- Respiratory Syncytial Virus
- Retic Count
- Reticulocyte Count
- Reticulocyte Index
- Retinol
- Rheumatoid Factor
- Ristocetin Cofactor
- Rubella Test
- Rubella antibodies, IgM and IgG
- Rubeola