| Ci - Cn | Nummer |
| Cichorium intybus und Cichorium endivia | 18 |
| Cicuta virosa | 8 |
| Cicutoxin | 14 / 8 |
| Ciguatoxin | 14 |
| Cimetidin | 14 / 18 |
| Cimetropiumbromid | 1 |
| Cimicifuga racemosa | 14 |
| Cina | |
| Cinchocain | 16 / gelegentlich 18 |
| Cinchomeronsäure | 16 |
| Cinchona pubescens | 14 |
| Cinchonidin | xxx |
| (-)-Cinchonidin | 14 |
| Cinchonin | xxx |
| (+)-Cinchonin | 14 |
| Cinchophen | |
| Cinchovatin | |
| Cinerarie | # 227 + |
| Cinerin-I | 14 |
| Cinerin-II | |
| Cinidonethyl | 16 / 18 |
| Cinnamal | 14 / gelegentlich 18 |
| Cinnamomum camphora | 14 |
| Cinnamomum zeylanicum | 18 |
| 6’-Cinnamoylcatalpol | 16 |
| Cinnamylalkohol | 14 / schwach 18 |
| Cinnamylidenaceton | xxx |
| Ciprofloxacin | 14 / 18 |
| Citraconsäureanhydrid | 16 / 18 |
| Citral | 16 / selten 18 |
| Citrinin | 14 / 19a |
| Citronellal | Selten 18 |
| Citronellol | 16 / 18 |
| Citronellöl | |
| Citronenöl | 16 |
| Citronensäure | |
| Citronensäure-Calciumsalz | 12 |
| Citronensäure-Kaliumsalz | 16 |
| Citronensäure-Natriumsalz | |
| Citronensäure-Piperazinsalz | 16 / 13 / 19 |
| Citrullus colocynthis | 16 |
| Citrus aurantium | # 227 H |
| Citrusöle | # 32 Photo |
| Citrus sinensis | 18 |
| Cladonia stellaris | 18 |
| Cladosporium herbarum | # (19a) |
| Clarithromycin | xxx |
| Clark-1 | xxx |
| Clark-H | xxx |
| Claviceps purpurea | 1 |
| Claviformin | 14 / # (19c) |
| Clelands Reagenz | 16 |
| Clematisalpina | 14 |
| Clematisrecta | |
| Clematis vitalba | 16 |
| Cleome spinosa | |
| Clenbuterol | xxx |
| Clethodim | 16 |
| Climbazol | |
| Clindamycin | xxx |
| Clioquinol | xxx |
| Clitocybe-Arten | 16 |
| Clivia miniata | |
| Clobazam | 17 |
| Clobutinol | xxx |
| Clodinafop-propargyl | 16 / 18 |
| Clofenamidum | 16 |
| Clofentezin | 14 |
| Clofop-isobutyl | xxx |
| Cloforex | 16 |
| Clomazone | |
| Clomethiazol | xxx |
| Clominorex | 16 |
| Clomipramin | xxx |
| Clonazepam | 17 |
| Clonidin | xxx |
| Clonidin-hydrochlorid | 14 / 15 |
| Clonitazen | 17 |
| Clonitralid | 14 |
| Clopyralid | 16 / # 6 Augen |
| Cloquintocet-mexyl | 16 / 18 |
| Clorazepat | 17 |
| Clotiazepam | |
| Cloxazolam | |
| Clozapin | xxx |
| C N | xxx |
| Cnicus benedictus | 18 |