Diagnosaurus
- Macrocytic anemia
- Macroglossia
- Magnesium, decreased serum
- Magnesium, increased serum
- MAHA
- Malabsorption
- Malar rash
- Malignant ascites
- Malingering
- Malnutrition
- Mania
- Manic depression
- Mastalgia
- Mediastinal mass
- Melena
- Memory loss
- Meningitis, carcinomatous
- Menopause
- Menorrhagia
- Menstrual bleeding, heavy
- Menstruation, painful
- Mental status, altered
- Metabolic acidosis, increased anion gap
- Metabolic acidosis, normal anion gap
- Metabolic alkalosis
- Metastases to bone
- Metastases to brain
- Metastases to heart
- Metastases to kidney
- Metastases to liver
- Metastases to lung
- Metastases to meninges
- Metastases to skin
- Metastases to spinal cord
- Methemoglobinemia
- Microalbuminuria
- Microangiopathic hemolytic anemia
- Microcytic anemia
- Migratory arthritis
- Morbilliform rash
- Mouth, dry
- Movement disorders
- Murmur, diastolic
- Murmur, systolic
- Muscle cramps
- Muscle pain
- Myalgia
- Myoclonus
- Myopathy
- Myositis