This code system http://terminology.hl7.org/CodeSystem/v2-0256 defines the following codes:
| Code | Display | Definition |
| BS | Baseline (time just before the challenge) | Baseline (time just before the challenge) |
| PEAK | The time post drug dose at which the highest drug level is reached (differs by drug) | The time post drug dose at which the highest drug level is reached (differs by drug) |
| TROUGH | The time post drug dose at which the lowest drug level is reached (varies with drug) | The time post drug dose at which the lowest drug level is reached (varies with drug) |
| RANDOM | Time from the challenge, or dose not specified. (random) | Time from the challenge, or dose not specified. (random) |
| 1M | 1 minute post challenge | 1 minute post challenge |
| 2M | 2 minutes post challenge | 2 minutes post challenge |
| 3M | 3 minutes post challenge | 3 minutes post challenge |
| 4M | 4 minutes post challenge | 4 minutes post challenge |
| 5M | 5 minutes post challenge | 5 minutes post challenge |
| 6M | 6 minutes post challenge | 6 minutes post challenge |
| 7M | 7 minutes post challenge | 7 minutes post challenge |
| 8M | 8 minutes post challenge | 8 minutes post challenge |
| 9M | 9 minutes post challenge | 9 minutes post challenge |
| 10M | 10 minutes post challenge | 10 minutes post challenge |
| 15M | 15 minutes post challenge | 15 minutes post challenge |
| 20M | 20 minutes post challenge | 20 minutes post challenge |
| 25M | 25 minutes post challenge | 25 minutes post challenge |
| 30M | 30 minutes post challenge | 30 minutes post challenge |
| 1H | 1 hour post challenge | 1 hour post challenge |
| 2H | 2 hours post challenge | 2 hours post challenge |
| 2.5H | 2 1/2 hours post challenge | 2 1/2 hours post challenge |
| 3H | 3 hours post challenge | 3 hours post challenge |
| 4H | 4 hours post challenge | 4 hours post challenge |
| 5H | 5 hours post challenge | 5 hours post challenge |
| 6H | 6 hours post challenge | 6 hours post challenge |
| 7H | 7 hours post challenge | 7 hours post challenge |
| 8H | 8 hours post challenge | 8 hours post challenge |
| 8H SHIFT | 8 hours aligned on nursing shifts | 8 hours aligned on nursing shifts |
| 12H | 12 hours post challenge | 12 hours post challenge |
| 24H | 24 hours post challenge | 24 hours post challenge |
| 2D | 2 days | 2 days |
| 3D | 3 days | 3 days |
| 4D | 4 days | 4 days |
| 5D | 5 days | 5 days |
| 6D | 6 days | 6 days |
| 7D | 7 days | 7 days |
| 1W | 1 week | 1 week |
| 10D | 10 days | 10 days |
| 2W | 2 weeks | 2 weeks |
| 3W | 3 weeks | 3 weeks |
| 4W | 4 weeks | 4 weeks |
| 1L | 1 month (30 days) post challenge | 1 month (30 days) post challenge |
| 2L | 2 months (60 days) post challenge | 2 months (60 days) post challenge |
| 3L | 3 months (90 days) post challenge | 3 months (90 days) post challenge |