| Condurango cortex | | Herbal remedies | 1 |
| Coneflower tincture | | Herbal remedies | 1 |
| Conestat alfa | 80295-38-1 | Hemostatics | 1 |
| Conjugated Estrogen | 12126-59-9 | | 1 |
| Copper (II) carbonate basic | 12069-69-1 | Minerals and electrolytes | 1 |
| Copper (II) oxide | 1317-38-0 | Minerals and electrolytes | 1 |
| Copper gluconate | 527-09-3 | | 1 |
| Copper tetraMIBI tetrafluoroborate | 103694-84-4 | | 1 |
| Copper(II) chloride dihydrate | 10125-13-0 | | 1 |
| Coriander | | Herbal remedies | 1 |
| Couch grass | | Herbal remedies | 1 |
| Cowslip flower | | Herbal remedies | 1 |
| CpG 1018 ODN | 112732-17-9 | Immunostimulants | 1 |
| CpG 7909 ODN | 2647530-73-0 | Immunostimulants | 1 |
| Crizotinib intermediates | 877399-74-1 | | 1 |
| Crospovidone (PVPP) | 9003-39-8 | | 1 |
| Cumin fruits powder | | Herbal remedies | 1 |
| Cumin seed | | Herbal remedies | 1 |
| Cupric Chloride | 7447-39-4 | Minerals and electrolytes | 1 |
| Cyanamide | 420-04-2 | Other substances | 1 |
| Cyclic Adenosine Monophosphate | 60-92-4 | Other substances | 1 |
| Cyclopentanone | 120-92-3 | | 1 |
| Cyclopentyl Mandelic Acid | 427-49-6 | Diuretics | 1 |
| Cyclopropane Methanol | 2516-33-8 | Intravenous anesthetics | 1 |
| Cyclopropyl bromide | 4333-56-6 | | 1 |
| Cyclopropyl-1-Piperazinylmethanone As Hcl | 59878-57-8 | Intermediates | 1 |
| Cyclopropylmethyl Bromide | 7051-34-5 | Other substances | 1 |
| Cytidine Diphosphate Trisodium | 203787-91-1 | | 1 |
| D-Asparagine | 2058-58-4 | Other substances | 1 |
| D-Cloprostenol sodium | 62561-03-9 | | 1 |
| D-Cysteine | 921-01-7 | Other substances | 1 |
| D-Glutamic Acid | 6893-26-1 | Other substances | 1 |
| D-Leucine | 328-38-1 | Other substances | 1 |
| D-Proline | 344-25-2 | Other substances | 1 |
| D-Xylitol | 488-81-3 | Other substances | 1 |
| D-isomer Levofloxacin | 59319-72-1 | Quinolones | 1 |
| Dabigatran Etexilate Mesylate | 872728-81-9 | | 1 |
| Dabrafenib + Trametinib | | | 1 |
| Dacomitinib | 1110813-31-4 | | 1 |
| Damiana herb | | Herbal remedies | 1 |