- Lone star fever 082.8
- Loneliness V62.89
- Long labor 662.1
- Long-term (current) drug use V58.69
- Longitudinal stripes or grooves, nails 703.8
- Loop
- Loose - see also condition
- Loosening epiphysis 732.9
- Looser (-Debray)-Milkman syndrome (osteomalacia with pseudofractures) 268.2
- Lop ear (deformity) 744.29
- Lorain's disease or syndrome (pituitary dwarfism) 253.3
- Lorain-Levi syndrome (pituitary dwarfism) 253.3
- Lordosis (acquired) (postural) 737.20
- Loss
- Lou Gehrig's disease 335.20
- Louis-Bar syndrome (ataxia-telangiectasia) 334.8
- Louping ill 063.1
- Lousiness - see Lice
- Low
- Lowe (-Terrey-MacLachlan) syndrome (oculocerebrorenal dystrophy) 270.8
- Lower extremity - see condition
- Lown (-Ganong)-Levine syndrome (short P-R interval, normal QRS complex, and paroxysmal supraventricular tachycardia) 426.81
