- Median - see also condition
- Mediastinal shift 793.2
- Mediastinitis (acute) (chronic) 519.2
- Mediastinopericarditis (see also Pericarditis) 423.9
- Mediastinum, mediastinal - see condition
- Medical services provided for - see Health, services provided because (of)
- Medicine poisoning (by overdose) (wrong substance given or taken in error) 977.9
- Medin's disease (poliomyelitis) 045.9
- Mediterranean
- Medulla - see condition
- Medullary
- Medullated fibers
- Medulloblastoma (M9470/3)
- Medulloepithelioma (M9501/3) - see also Neoplasm, by site, malignant
- Medullomyoblastoma (M9472/3)
- Meekeren-Ehlers-Danlos syndrome 756.83
- Megacaryocytic - see condition
- Megacolon (acquired) (functional) (not Hirschsprung's disease) 564.7
- Megaduodenum 537.3
- Megaesophagus (functional) 530.0
- Megakaryocytic - see condition
- Megalencephaly 742.4