Diagnosaurus
- Hair loss
- Hairy cell leukemia
- Hallucinations
- Hansen's disease
- Hantaviruses
- Hay fever
- HDL decreased
- Headache
- Headache, cough-associated
- Headache, migraine
- Hearing loss
- Heart failure
- Heart failure, right-sided
- Heart metastases
- Heat rash
- HELLP syndrome
- Hematocrit, decreased
- Hematocrit, increased
- Hemochromatosis
- Hemolytic anemia
- Hemolytic anemia, microangiopathic
- Hemolytic uremic syndrome
- Hemophilia
- Hemorrhoids
- Henoch-Schonlein purpura
- Hepatic encephalopathy
- Hepatic failure, acute
- Hepatic vein obstruction
- Hepatitis, acute
- Hepatitis, alcoholic
- Hepatitis, chronic
- Hepatocellular carcinoma
- Herniated lumbar disk
- Heroin overdose
- Herpes simplex
- Herpes zoster
- Histoplasmosis
- HIV & AIDS
- HIV and renal failure
- HIV-associated nephropathy
- Hives
- Hodgkin's disease
- Homocystinuria
- Hookworm disease
- Hordeolum
- Horner's syndrome
- Hospital-acquired pneumonia
- Huntington's disease
- Hydatid disease
- Hydrocele
- Hydrocephalus, normal pressure
- Hyperaldosteronism, primary
- Hypercalcemia
- Hypercholesterolemia
- Hypercoagulable state
- Hypercortisolism
- Hyperglycemia
- Hyperglycemic hyperosmolar state
- Hyperhidrosis
- Hyperkalemia
- Hypermagnesemia
- Hypernatremia
- Hyperosmotic nonketotic coma
- Hyperparathyroidism
- Hyperphosphatemia
- Hyperprolactinemia
- Hypersensitivity (leukocytoclastic) vasculitis
- Hypersensitivity pneumonitis
- Hypersomnia
- Hypertension
- Hypertension, pulmonary
- Hypertension, secondary
- Hyperthermia
- Hyperthyroidism
- Hypertriglyceridemia
- Hypertrophic obstructive cardiomyopathy (HOCM)
- Hyperuricemia, endogenous
- Hyperventilation
- Hypocalcemia
- Hypoglycemia
- Hypogonadism, female
- Hypogonadism, male
- Hypokalemia
- Hypomagnesemia
- Hyponatremia
- Hypoparathyroidism
- Hypophosphatemia
- Hypopituitarism
- Hypotension
- Hypothermia
- Hypothermia of extremities
- Hypothyroidism
- Hypoventilation, chronic