How to read a ClinicalTrials.gov record

Most reporting about trials is downstream of one public database. Reading it yourself is more useful than any summary, including ours.

The fields that carry the most meaning

NCT number. The unique identifier. Quote it and anyone can find exactly the study you mean.

Status. Recruiting, active but not recruiting, completed, terminated, withdrawn. Terminated means it started and stopped early; withdrawn means it never enrolled anyone. Neither necessarily implies the treatment failed — funding and enrolment problems end trials too.

Phase. Phase 1 asks mainly about safety and dose. Phase 2 looks for a signal of benefit. Phase 3 compares against current standard care at scale. Phase 4 happens after approval. In cardiovascular research a large share of records carry no phase at all, because so much of the work is observational.

Enrolment. Check whether it says actual or estimated. An estimate on a planned study is a target, not a fact.

Primary outcome measure. The most informative field and the most skipped. It states what the study set out to show and over what period. In cardiovascular trials, watch whether the primary outcome is a hard endpoint such as death or hospitalisation, or a surrogate such as a change in a blood measurement. The two support very different claims.

What the registry will not tell you

It is not primarily a results database. Many studies post results late or not at all, and a registration is a plan rather than a finding.

Start here: the registry search.

Counts taken from the ClinicalTrials.gov API on 7 October 2026, covering studies with a registered start date on or after 1 July 2026. Registry numbers move as records are added and updated, so treat them as a snapshot rather than a fixed figure.