| Normochromic | Blood | Hematology and Cell counts | LP393446-2 | 1 |
| Nortriptyline | LP14984-6 | 1 |
| Nortriptyline | Serum or Plasma | Drug toxicology | LP391155-1 | 1 |
| NSAIDS | LP31430-9 | 1 |
| Nucleated cells | LP65367-2 | 1 |
| Nucleated cells | Sputum | Hematology and Cell counts | LP420349-5 | 1 |
| Observation | Bone marrow | Microbiology | LP443037-9 | 1 |
| Observation | Tissue and Smears | Microbiology | LP443079-1 | 1 |
| Octadecanoate (C18:0) | Red Blood Cells | Chemistry - non-challenge | LP382076-0 | 1 |
| Octadecanoate (C18:0) | Serum or Plasma | Chemistry - non-challenge | LP382077-8 | 1 |
| Octadecatetraenoate (C18:4w3) | LP201769-9 | 1 |
| Octadecatetraenoate (C18:4w3) | Serum or Plasma | Chemistry - non-challenge | LP382130-5 | 1 |
| Octanoate (C8:0) | Red Blood Cells | Chemistry - non-challenge | LP382058-8 | 1 |
| Octanoate (C8:0) | Serum or Plasma | Chemistry - non-challenge | LP382059-6 | 1 |
| Octanoylcarnitine (C8) | Serum or Plasma | Chemistry - non-challenge | LP381733-7 | 1 |
| Octenoylcarnitine (C8:1) | DBS | Chemistry - non-challenge | LP381761-8 | 1 |
| Octenoylcarnitine (C8:1) | Serum or Plasma | Chemistry - non-challenge | LP381763-4 | 1 |
| Odor | LP31914-2 | 1 |
| Odor | Urine | Specimen information | LP404252-1 | 1 |
| Oleate (C18:1w9) | Red Blood Cells | Chemistry - non-challenge | LP382100-8 | 1 |
| Oleate (C18:1w9) | Serum or Plasma | Chemistry - non-challenge | LP382101-6 | 1 |
| Oleoylcarnitine (C18:1) | DBS | Chemistry - non-challenge | LP381949-9 | 1 |
| Oleoylcarnitine (C18:1) | Serum or Plasma | Chemistry - non-challenge | LP381951-5 | 1 |
| Oligosaccharides | LP18038-7 | 1 |
| Oligosaccharides | Urine | Chemistry - non-challenge | LP385596-4 | 1 |
| Omega 3 fatty acids (w3) | Serum or Plasma | Chemistry - non-challenge | LP382109-9 | 1 |
| Oncology drugs | LP31428-3 | 1 |
| Organic acidemia conditions suspected | LP97723-8 | 1 |
| Organic acidemia conditions suspected | DBS | Chemistry - non-challenge | LP417004-1 | 1 |
| Organic acidemias | DBS | Chemistry - non-challenge | LP385854-7 | 1 |
| Organic acids pattern | Serum or Plasma | Chemistry - non-challenge | LP416967-0 | 1 |
| Organic acids pattern | Urine | Chemistry - non-challenge | LP416968-8 | 1 |
| Ornithine | Amniotic fluid | Chemistry - non-challenge | LP384199-8 | 1 |
| Ornithine | Cerebral spinal fluid | Chemistry - non-challenge | LP384203-8 | 1 |
| Ornithine | DBS | Chemistry - non-challenge | LP384201-2 | 1 |
| Ornithine | Serum or Plasma | Chemistry - non-challenge | LP384205-3 | 1 |
| Orotate | Cerebral spinal fluid | Chemistry - non-challenge | LP383527-1 | 1 |
| Orotate | Serum or Plasma | Chemistry - non-challenge | LP383528-9 | 1 |
| Orotate | Urine | Chemistry - non-challenge | LP383529-7 | 1 |
| Orotidine | Cerebral spinal fluid | Chemistry - non-challenge | LP383535-4 | 1 |
| Orotidine | Serum or Plasma | Chemistry - non-challenge | LP383536-2 | 1 |
| Orotidine | Urine | Chemistry - non-challenge | LP383537-0 | 1 |
| Osmol gap | LP172681-1 | 1 |
| Osmol gap | Stool | Chemistry - non-challenge | LP386599-7 | 1 |
| Osmotic fragility beginning hemolysis | LP65752-5 | 1 |
| Osmotic fragility beginning hemolysis | Red Blood Cells | Hematology and Cell counts | LP393820-8 | 1 |
| Osmotic fragility full hemolysis | LP65753-3 | 1 |
| Osmotic fragility full hemolysis | Red Blood Cells | Hematology and Cell counts | LP393821-6 | 1 |
| Osteocalcin | LP15759-1 | 1 |
| Osteocalcin | Serum or Plasma | Chemistry - non-challenge | LP386040-2 | 1 |
| Other cells | Amniotic fluid | Hematology and Cell counts | LP433121-3 | 1 |
| Other cells | Blood cord | Hematology and Cell counts | LP393305-0 | 1 |
| Other cells | Cerebral spinal fluid | Hematology and Cell counts | LP393307-6 | 1 |
| Other cells | Synovial fluid | Hematology and Cell counts | LP393310-0 | 1 |
| Other elements | LP99280-7 | 1 |
| Other elements | Urine sediment | Urinalysis | LP402521-1 | 1 |
| Ova and parasites | XXX | Microbiology | LP442165-9 | 1 |
| Oval macrocytes | LP14572-9 | 1 |
| Oval macrocytes | Blood | Hematology and Cell counts | LP393435-5 | 1 |
| Ovalocytes | LP17644-3 | 1 |
| Ovalocytes | Blood | Hematology and Cell counts | LP393409-0 | 1 |
| Oxalate | Calculus (stone) | Chemistry - non-challenge | LP386325-7 | 1 |
| Oxalate | Serum or Plasma | Chemistry - non-challenge | LP386328-1 | 1 |
| OXcarbazepine | Serum or Plasma | Drug toxicology | LP390808-6 | 1 |
| Oxygen | Body fluid | Chemistry - non-challenge | LP383368-0 | 1 |
| Oxygen content | Blood | Chemistry - non-challenge | LP383373-0 | 1 |
| Oxygen content | Blood capillary | Chemistry - non-challenge | LP383375-5 | 1 |
| Oxygen content | Blood central venous | Chemistry - non-challenge | LP426944-7 | 1 |
| Oxygen content | Blood cord | Chemistry - non-challenge | LP383376-3 | 1 |
| Oxygen content | Blood mixed venous | Chemistry - non-challenge | LP383379-7 | 1 |
| Oxyhemoglobin | Cerebral spinal fluid | Chemistry - non-challenge | LP383419-1 | 1 |
| Oxyhemoglobin | Plasma | Chemistry - non-challenge | LP383420-9 | 1 |
| Palatinase | Small intestine Tissue | Chemistry - non-challenge | LP383163-5 | 1 |
| Palatinase | Tissue and Smears | Chemistry - non-challenge | LP383162-7 | 1 |
| Palmitate (C16:0) | Red Blood Cells | Chemistry - non-challenge | LP382072-9 | 1 |
| Palmitate (C16:0) | Serum or Plasma | Chemistry - non-challenge | LP382073-7 | 1 |
| Palmitoleate (C16:1w7) | Red Blood Cells | Chemistry - non-challenge | LP382090-1 | 1 |
| Palmitoleate (C16:1w7) | Serum or Plasma | Chemistry - non-challenge | LP382091-9 | 1 |
| Palmitoleylcarnitine (C16:1) | DBS | Chemistry - non-challenge | LP381913-5 | 1 |
| Palmitoleylcarnitine (C16:1) | Serum or Plasma | Chemistry - non-challenge | LP381916-8 | 1 |
| Palmitoyl protein thioesterase | DBS | Chemistry - non-challenge | LP383164-3 | 1 |
| Palmitoyl protein thioesterase | Fibroblast | Chemistry - non-challenge | LP383165-0 | 1 |
| Palmitoyl protein thioesterase | White blood cells | Chemistry - non-challenge | LP383167-6 | 1 |
| Palmitoylcarnitine (C16) | DBS | Chemistry - non-challenge | LP381883-0 | 1 |
| Palmitoylcarnitine (C16) | Serum or Plasma | Chemistry - non-challenge | LP381886-3 | 1 |
| Pappenheimer bodies | LP17682-3 | 1 |
| Pappenheimer bodies | Blood | Hematology and Cell counts | LP393393-6 | 1 |
| Parainfluenza virus | LP18337-3 | 1 |
| Parainfluenza virus | XXX | Microbiology | LP444700-1 | 1 |
| Parasites | Urine sediment | Urinalysis | LP402506-2 | 1 |
| Parathyrin related protein | LP15776-5 | 1 |
| Parathyrin related protein | Serum or Plasma | Chemistry - non-challenge | LP386042-8 | 1 |
| Parathyrin.intact | Serum or Plasma | Chemistry - non-challenge | LP381353-4 | 1 |
| Parathyrin.intact intraoperative percent change | LP149576-3 | 1 |
| Parathyrin.intact intraoperative percent change | Serum or Plasma | Chemistry - non-challenge | LP381355-9 | 1 |
| Parathyrin.mid molecule | LP15779-9 | 1 |
| Parathyrin.mid molecule | Serum or Plasma | Chemistry - non-challenge | LP381356-7 | 1 |
| Pathologist review | LP18649-1 | 1 |
| Pathologist review | Blood | Blood bank | LP399311-2 | 1 |
| Pathology biopsy report | LP121003-0 | 1 |