| Abbreviation | Term(s) |
| Sacral spine | S-Spine |
| Sacral vertebrae | S1-S5 |
| Salpinggo-oophorectomy | SO |
| Sarcoma | SARC |
| Sedimentation rate | SR |
| Sequential multiple analysis (Biochem profile) | SMA |
| Serum glutamic oxaloacetic transaminase | SGPT |
| Serum hepatitis | SH |
| Shortness of breath | SOB |
| Silver nitrate | AGNO3 |
| Skilled nursing facility | SNF |
| Small | SM, SML |
| Small bowel | SML BWL |
| Small bowel | SB |
| Social history | SH |
| Solution | SOL |
| Special lymphocytes formed in bone marrow (derived from bursa of Fabricius) | B-CELLS |
| Specific gravity | SP GR |
| Specimen | SPEC |
| Split thickness skin graft | STSG |
| Squamous | SQ, SQUAM |
| Squamous cell carcinoma | SCC |
| Squamous cell carcinoma | SQCELL CA |
| Staphylococcus | STAPH |
| Status post | S/P |
| Streptococcus | STREP |
| Subacute bacterial endocarditis | SBE |
| Subcutaneous | S-Q, SQ |
| Subcutaneous | SUB-Q, SUBQ |
| Superior vena cava | SVC |
| Surgery, surgical | SURG |
| Symptoms | SX |