Internal medicine is the study of diseases that affect the body's internal organs, such as the heart, lungs, liver, digestive system, kidneys, urinary tract, brain, spinal column, nerves, muscles, and joints. Even though some diseases only affect one organ, most common diseases, such as arteriosclerosis, diabetes, high blood pressure, and cancer, can affect more than one organ.

Cardiovascular diseases (heart failure, coronary artery disease, hyperlipidaemia, and hypertension)
Gastro-intestinal diseases
Endocrine diseases (diabetes mellitus, goitre, hyperthyroidism, hypothyroidism)
Kidney diseases (acute and chronic renal failure, urinary tract disorders)
Haematological disorders (anaemia, bleeding disorders)
Rheumatic diseases (arthritis, cardiac rheumatism, Mediterranean fever, rheumatic diseases)
Infectious diseases