| Test Name (Click to sort by popular result) | COE Code |
| MDMA (Ecstasy), Urine | ML MISC |
| Magnesium, Erythrocytes | RBCMAG |
| Magnesium, Serum | MAG |
| Magnesium, Urine | MAGU/MAGQ |
| Malaria Smear | GIEMSA |
| Manganese, Serum/Urine | MN-S/MN-U |
| Medium Chain Acyl-CoA Dehydrogenase Deficiency, Molecular Profile | ML MISC |
| Meprobamate, Serum | ML MISC |
| Mercaptopurine | MERCAP |
| Mercury, Blood/Urine | HG-B/HG-U |
| Metanephrines and Normetanephrines, Fractionation | METAN |
| Metanephrines and Normetanephrines, Plasma | PMET |
| Methadone, Serum | ML MISC |
| Methadone, Urine | UMETHAD/METHG/SENDOUT |
| Methaqualone, Plasma | ML MISC |
| Methaqualone, Urine | GCMS |
| Methemoglobin, Whole Blood, Adult | |
| Methemoglobin, Whole Blood, Pediatric | |
| Methotrexate | MTX |
| Methsuximide, Serum | ML MISC |
| Methylenetetrahydrofolate Reductase C677T Mutation Detection | MLABEL |
| Methylmalonic Acid, Serum | MMAS |
| Methylmalonic Acid, Urine | MMAU |
| Methylphenidate (Ritalin) | ML MISC |
| Mexiletine | ML MISC |
| Microalbumin, Urine | UMA |
| Microfilaria Smear | GIEMSA |
| Microsatellite Instability Analysis | MLABEL |
| Microsporidia Exam | OPM |
| Miscellaneous Unspecified | |
| Mitochondrial Antibody | MITO |
| Mitotane (Lysodren) | ML MISC |
| Molecular Genetics Clinical Identification of a Familial Mutation | CLIFSS |
| Molecular Genetics Clinical Verification of Research Results | CLVRSS |
| Molecular Genetics Parental Analysis of CMA Result | CMAPAS |
| Monoclonal Gammopathy Evaluation | MGE |
| Motilin | FMOT |
| Mucopolysaccharides Screen, Urine | MPSSCR |
| Mumps Virus Antibody, IgG | MUMPGT |
| Mumps Virus Antibody, IgM | |
| Muscle Biopsy | |
| Myasthenia Gravis Evaluation, Adult | MGEA |
| Myasthenia Gravis Evaluation, Lambert-Eaton Syndrome | ML MISC |
| Myasthenia Gravis Evaluation, Pediatric | ML MISC |
| Myasthenia Gravis Evaluation, Thymoma | ML MISC |
| Mycobacterium tuberculosis Complex by PCR, Respiratory | ML MISC |
| Mycobacterium tuberculosis DNA by PCR, Non-Respiratory | SL MISC |
| Mycophenolic Acid | MPA |
| Mycoplasma hominis Culture | MYCOH |
| Mycoplasma pneumoniae Antibody | MYCOP |
| Mycoplasma pneumoniae Culture | MYCOPN |
| Myelin Basic Protein, CSF | MBPC |
| Myeloperoxidase Antibodies | MYELO |
| Myocardial Antibodies | MCA |
| Myoglobin, Serum | MYO |
| Myoglobin, Urine | UMYO |
| Myositis Associated Antibodies (MAA) | MYOSIT |