| RABI | Rabies Antibody Screen | — |
| RBCBAND | RBC Band 3 Protein Reduction in Hereditary Spherocytosis | — |
| FORB | RBC Folate | — |
| RBCME | Red Blood Cell Membrane Evaluation, Blood | — |
| RENFP | Renal Function Panel | Please see individual components for methodology |
| REN | Renin Activity | — |
| REPTL | Reptilase Time with Reflex to Reptilase Time 1:1 Mix | — |
| RESP | Respiratory Panel Inf A/B, RSV, COVID | Respiratory Panel Inf A/B, RSV, COVID |
| RESPP | Respiratory Pathogen Panel by PCR | — |
| RVDFA | Respiratory Viruses, DFA | — |
| RTIH1 | Reticulocyte Count | Fluorescent Flow Cytometry; DC Impedance with Hydrodynamic Focusing; Cyanide-Free SLS Method |
| RBP | Retinol Binding Protein | — |
| REVT3 | Reverse T3 (RPS) | — |
| RFPS | Rheumatoid Factor | Particle-Enhanced Immunoturbidimetric Assay |
| RFFO | Rheumatoid Factor Body Fluid | — |
| RFPAN | Rheumatoid Factors, IgA, IgG & IgM by ELISA | — |
| FRDG | Rhodotorula, IgE | — |
| RPPA | Ribosomal P Protein Antibody | — |
| RICE | Rice IgE | — |
| RIFAM | Rifampin Level, Ser/Plas | — |
| RISAP | Risankizumab Quantitation with Antibodies | — |
| ROMA | Risk of Ovarian Malignancy Algorithm | — |
| RISP | Risperidone and Metabolite | — |
| RIT | Ritalin (Methylphenidate) | — |
| RITUX | Rituxan Therapy Panel (CD3, CD19, CD20) | — |
| RIVAR | Rivaroxaban, Anti-Xa, Plasma | — |
| RNAP3 | RNA Polymerase III AB, IgG | — |
| RNPABS | RNP (Ribonucleic Protein) (ENA) Antibody, IgG | — |
| RMSG | Rocky Mountain Spotted Fever (Rickettsia) IgG | — |
| RSFGM | Rocky Mountain Spotted Fever (Rickettsia) IgG & IgM | — |
| RMSM | Rocky Mountain Spotted Fever (Rickettsia) IgM | — |
| AGROTA | Rotavirus Antigen | Qualitative Enzyme Immunoassay (EIA) |
| RPRR | RPR | — |
| RPRQR | RPR, Quantitative | — |
| RBPG | Rubella Abs, IgG Serum | — |
| RUBIGG | Rubella Antibody, IgG | Electrochemiluminescence Immunoassay |
| RUBMT | Rubella Antibody, IgM | — |
| RUFIN | Rufinamide | — |
| RUNX1 | RUNX1-RUNX1T1 (AML1-ETO) t(8;21) Detection, Quantitation | — |
