M
- Macular degeneration, dry
- Macular degeneration, wet
- Mad cow disease
- Major depressive disorder
- Malaria
- Male breast cancer
- Male hypogonadism
- Male infertility
- Malignant fibrous histiocytoma
- Malignant hyperthermia
- Malignant mesothelioma
- Malignant peripheral nerve sheath tumors (MPNST)
- Mallet toe and hammertoe
- MALS
- Mammary duct ectasia
- Manic-depressive illness
- Mantle cell lymphoma
- Marfan syndrome
- Marginal zone lymphoma
- MASH
- MASLD
- Mastalgia
- Mastitis
- MCAD deficiency
- mCRPC
- MD
- MDS
- ME/CFS
- Measles
- Measles, German
- Medial epicondylitis
- Medial tibial stress syndrome
- Median arcuate ligament syndrome (MALS)
- Medication overuse headaches
- Mediterranean anemia
- Medulloblastoma
- Megacolon
- Megaloblastic anemia
- Melanoma
- Melanoma of the eye
- MEN 2
- Meniere’s disease
- Meningioma
- Meningitis
- Meniscus tear
- Menopause
- Menorrhagia
- Menstrual cramps
- Mental illness
- Meralgia paresthetica
- Merkel cell carcinoma
- Mesenteric ischemia
- Mesenteric lymphadenitis
- Mesothelioma
- Metabolic dysfunction-associated steatohepatitis
- Metabolic dysfunction-associated steatotic liver disease
- Metabolic syndrome
- Metachromatic leukodystrophy
- Metastatic (stage 4) prostate cancer
- Metastatic castration-resistant prostate cancer (mCRPC)
- Metastatic colorectal cancer
- Metatarsalgia
- Methicillin-resistant staphylococcus aureus infection
- MFS
- MG
- MGUS
- Microcephaly
- Microscopic colitis
- Microscopic hematuria
- Migraine
- Migraine with aura
- Mild cognitive impairment (MCI)
- Miliaria
- Milk allergy
- Milk intolerance
- Miscarriage
- MISME
- Mitral valve disease
- Mitral valve prolapse
- Mitral valve regurgitation
- Mitral valve stenosis
- Mittelschmerz
- Mixed connective tissue disease
- MOG antibody-associated disorder
- MOGAD
- Molar pregnancy
- Mold allergy
- Moles
- Molluscum contagiosum
- Mono
- Monoclonal gammopathy of undetermined significance (MGUS)
- Mononucleosis
- Mood disorders
- Morning sickness
- Morphea
- Morton neuroma
- Mosquito bites
- Mouth cancer
- Movement disorders
- Moyamoya disease
- MRSA infection
- MS
- MSA
- Mucocutaneous lymph node syndrome
- Multiple endocrine neoplasia type 1
- Multiple endocrine neoplasia, type 1 (MEN 1)
- Multiple endocrine neoplasia, type 2 (MEN 2)
- Multiple inherited schwannomas, meningiomas, and ependymomas
- Multiple myeloma
- Multiple sclerosis
- Multiple system atrophy
- Multisystem inflammatory syndrome in children (MIS-C)
- Mumps
- Munchausen syndrome
- Muscle cramp
- Muscle strains
- Muscular dystrophy
- Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)
- Myasthenia gravis
- Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD)
- Myelodysplastic neoplasms
- Myelodysplastic syndromes
- Myelofibrosis
- Myocardial infarction
- Myocardial ischemia
- Myocarditis
- Myoclonus
- Myofascial pain syndrome
- Myopia
- Myxofibrosarcoma
- MZL