# Fields, empty values and sources

Lesson 2 of [How to read an opioid treatment listing](https://opioidtreatment.fyi/academy/read-an-opioid-treatment-listing.md), 12 minutes.

Each listing has fields. This lesson explains the main ones. Medication offered The medication field can show methadone, buprenorphine or naltrexone. A value appears only when the provider or a public register states it. An empty field means unknown. It does not mean the service lacks that medicatio…

The rest of this lesson is for learners enrolled in the course. [See how How to read an opioid treatment listing works](https://opioidtreatment.fyi/academy/read-an-opioid-treatment-listing.md).

Also on the [web page](https://opioidtreatment.fyi/academy/read-an-opioid-treatment-listing/fields-and-sources).

> Talk to a doctor, pharmacist or other qualified clinician before you start, stop or change treatment. In an emergency call your local emergency number: 911 in the US and Canada (or call or text 988), 999 in the UK and Ireland (or call 111 in the UK, 112 in Ireland), 000 in Australia, 111 in New Zealand. For overdose, call emergency services first.