| Acetaminophen | Acetoacetic acid |
| Acetone | Adrenocorticotropic Hormone (ACTH) |
| Alanine | Acid phosphatase |
| Adenosine deaminase | Alanine aminotransferase |
| Albumin | Alcohol dehydrogenase |
| Aldolase | Aldosterone |
| Alkaline phosphatase | Alprazolam |
| Amikacin | Aluminum |
| α-Aminobutyric acid | δ-Aminolevulinic acid |
| Amiodarone | Amitriptyline |
| Ammonia (as nitrogen) | Amobarbital |
| Amphetamine | Amylase |
| Androstenedione | Angiotensin I |
| Angiotensin II | Angiotensin-converting enzyme |
| Anion gap | Antidiuretic hormone (ADH) |
| Antithrombin III | Alpha1 – Antitrypsin |
| Apolipoprotein A | Apolipoprotein B |
| Arginine | Arsenic |
| Asparagine | Aspartate aminotransferase (AST) |
| Aspartic acid | Atrial natriuretic hormone |
| Base excess | Bicarbonate |
| Bile acids | Bilirubin |
| Biotin | Bismuth |
| Bromide | C1 esterase inhibitor |
| C3 complement | C4 complement |
| Cadmium | Caffeine |
| Calcitonin | Calcium |
| Cancer antigen (CA) 125 | Carbamazepine |
| Carbon dioxide | Carboxyhemoglobin |
| Carcinoembryonic antigen (CEA) | Carotene |
| Carotenoids | Ceruloplasmin |
| Chloramphenicol | Chlordiazepoxide |
| Chloride | Chlorpromazine |
| Chlorpropamide | Cholesterol |
| Cholinesterase | Chromium |
| Citrate | Citrulline |
| Clonazepam | Clonidine |
| Clozapine | Coagulation factor I |
| Cobalt | Cocaine |
| Codeine | Coenzyme Q10 |
| Copper | Coproporphyrin |
| Corticotropin | Cortisol |
| Cotinine | C-peptide |
| C-reactive protein | Creatine |
| Creatine kinase | Creatinine |
| Creatinine clearance | Cyanide |
| Cyclic adenosine monophosphate | Cyclosporine |
| Cystine | D-dimer |
| Dehydroepiandrosterone (DHEA) | Dehydroepiandrosterone sulfate (DHEA-S) |
| Deoxycorticosterone | Desipramine |
| Diazepam | Digoxin |
| Diltiazem | Disopyramide |
| Dopamine | Doxepin |
| Dimethadione | Ephedrine |
| Epinephrine | Estradiol |
| Estriol | Estrone |
| Ethanol | Ethchlorvynol |