- Nail avulsion (traumatic removal of nail)
- Nail bruise (subungual hematoma)
- Nail laceration (nail bed cut)
- Nail contusion (swelling of finger and nail)
- Narcolepsy (uncontrollable sleeping)
- Narcotic (morphine, heroin) abuse
- Narcotic (morphine, heroin) overdose
- Nasal cancer (tumor)
- Nasal foreign body (unnatural object in the nose)
- Nasal fracture (broken nose)
- Nasal septum deviation
- Nasal polyps (growths)
- Nasopharyngeal carcinoma (tumor)
- Nasal trauma (injury)
- Near drowning
- Nearsightedness (myopia)
- Neck trauma (injury)
- Necrotizing fasciitis (life-threatening infection)
- Necrotizing enterocolitis (NEC)
- Necrotizing ulcerative gingivitis (NUG)
- Neisseria meningitidis infection (meningococcus, serious bacterial illness)
- Neisseria gonorrhea infection (sexually transmitted disease)
- Neuralgia (nerve pain)
- Neurofibromatosis (inherited nerve tumors)
- Neuroblastoma
- Neurogenic bladder (bladder paralysis)
- Neutropenia
- Newborn jaundice (newborn skin discoloration)
- Night blindness (nyctalopia)
- Night terrors (nightmares)
- Non venomous snake bite
- Nonsteroidal anti-inflammatory drug overdose (Motrin, Advil)
- Normal menstruation
- Norovirus infection (viral diarrhea, Norwalk virus))
- Nose bleed (epistaxis)
- Nursemaid's elbow (radial head subluxation)