- Misdirection
- Mismanagement, feeding 783.3
- Misplaced, misplacement
- Missed
- Misshapen reconstructed breast 612.0
- Missing - see also Absence
- Misuse of drugs NEC (see also Abuse, drug, nondependent) 305.9
- Mitchell's disease (erythromelalgia) 443.82
- Mite(s)
- Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS syndrome) 277.87
- Mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE) 277.87
- Mitral - see condition
- Mittelschmerz 625.2
- Mixed - see condition
- Mljet disease (mal de Meleda) 757.39
- Mobile, mobility
- Mobitz heart block (atrioventricular) 426.10
- Möbius'
- Moeller (-Barlow) disease (infantile scurvy) 267
- Mohr's syndrome (types I and II) 759.89
- Mola destruens (M9100/1) 236.1
- Molar pregnancy 631.8