- Macular degeneration
- Mad cow disease
- Magnesium test
- Magnetic resonance imaging scan
- Malaria
- Male breast cancer
- Male contraceptive pill
- Male-pattern hair loss
- Male thrush
- Malignant melanoma
- Malignant spinal cord compression
- Malnutrition
- Marfan syndrome
- Marine stings
- Mastalgia
- Mastectomy
- Mastitis
- Mastitis (non-breastfeeding)
- ME
- Measles
- Medial tibial stress syndrom
- Median nerve compression
- Medical research
- Medicines information
- Medium chain acyl dehydrogenase deficiency (MCADD)
- Meibomian cyst
- Melanoma
- Memory loss
- MenC vaccination
- Ménière’s disease
- Meningitis
- Menopause
- Menorrhagia
- Mesothelioma
- Metabolic syndrome
- Metatarsalgia
- Methicillin-resistant staphylococcus aureus
- Microalbumin test
- Migraine
- Miliaria
- Milk intolerance
- Mini-stroke
- Miscarriage
- MMR vaccination catch up campaign
- MMR vaccination
- Mobile phone safety
- Molar pregnancy
- Moles
- Molluscum contagiosum
- Mononucleosis
- Morning after pill
- Morning sickness
- Morton's neuroma
- Motion sickness
- Motor neurone disease
- Mountain sickness
- Mouth cancer
- Mouth ulcer
- MRI scan
- MRSA infection
- MS
- Mucositis
- Multi disciplinary team (cancer)
- Multiple sclerosis (MS)
- Mumps
- Munchausen’s syndrome
- Munchausen's syndrome by proxy
- Muscular dystrophy
- Myalgic encephalomyelitis
- Myasthenia gravis
- Myelodysplastic syndrome
- Myeloma
- Myocardial infarction
- Myopia