- MIF
- MIH
- MIS
- MMA
- MPA [may be referred to by drug names Mycophenolate mofetil or Mycophenolate sodium, or by drug brand names (CellCept, Ceptava, Myfortic, Myfenax)]
- MPO
- MPO-ANCA
- MRSA Screening
- MTHFR
- MTHFR DNA testing
- MTX
- Magnesium
- Mantoux (previously Heaf test)
- Manual differential
- Mast Cell Tryptase
- Mature Tryptase
- Maxtrex
- Measles and Mumps Tests
- Mercury
- Metadrenaline and normetadrenaline
- Metanephrine and normetanephrine
- Methofill
- Methotrexate
- Methyl salicylate
- Methylmalonic Acid
- Metoject
- Mg
- Micronutrients
- Mitochondrial Antibody
- Modigraf®
- Mono test
- Mononuclear heterophil test
- Mononucleosis spot test
- Monospot Test
- Mullerian inhibiting factor
- Mullerian-inhibiting hormone
- Mullerian-inhibiting substance
- Muscle nicotinic Acetylcholine Receptor (AChR) Binding Antibody
- Myasthenia Gravis Antibodies
- Mycology tests
- Mycophenolic Acid
- Mycoplasma
- Mycoplasma by PCR
- Mycoplasma culture
- Mycoplasma pneumoniae and Mycoplasma genitalium), Mycoplasma pneumoniae IgG and IgM antibodies, Mycoplasma culture (both M. pneumoniae and M. genitalium), Mycoplasma DNA testing (both M. pneumoniae and M. genitalium)
- Myoglobin Test
- molecular genetic testing