- Macular degeneration
- Mad Cow Disease
- Malaria
- Male Yeast Infection
- Malignancy see Cancer
- Marburg Virus
- Marfan Syndrome
- Measles
- Medical Informatics & Computers
- Medicinal Herbs see Herbal Medicine
- Melanoma
- Melasma
- Meniere's Disease
- Meningitis
- Menopause : Symptoms
- Mens Health
- Mental Disorders
- Meth
- Microbiology
- Migraine
- Miliaria
- Miscarriage
- Molluscum Contagiosum
- Monkeypox
- Mononucleosis
- Mosquitoes / Mosquito-borne diseases
- Mouth Cancer
- Mouth Disorders see Oral Diseases
- Mouth Sores
- Mucocutaneous lymph node syndrome see Kawasaki Disease
- Multiple Myeloma
- Multiple Sclerosis
- Mumps
- Myasthenia Gravis
- Mycoplasma Infections
- Myocardial Infarction see Heart Attack