Regulatory guide

How to read a ClinicalTrials.gov record: phases, status, dates and results

A field-by-field guide to ClinicalTrials.gov: what NCT numbers, phases, recruitment statuses, completion dates and the results tab tell you, and what they do not.

PharmaRadar360 Editorial · Published October 21, 2026 · 7 min read

Key points

Every registered study has an NCT number: “NCT” followed by eight digits. Use it to follow a trial across news, papers and filings.
Phase tells you the development stage; recruitment status tells you where the study is operationally. “Active, not recruiting” usually means treatment or follow-up is still going on.
The primary completion date is when data for the primary outcome are complete. It is the date that matters for topline results and for the results-reporting deadline.
For applicable trials and NIH-funded trials, results are due no later than one year after the primary completion date.
Records are submitted by sponsors. Treat them as the sponsor’s description, and check when the record was last updated.

Start with the NCT number

ClinicalTrials.gov, run by the US National Library of Medicine, assigns each registered study an identifier made of “NCT” and eight digits. Company releases, journal articles and regulatory documents usually cite it, which makes it the most reliable way to check that you are looking at the same study, because trial acronyms and titles are reused and changed.

Phase: how far along the product is

Drug trials are labelled Early Phase 1 through Phase 4; device and behavioural studies are usually “Not Applicable”. FDA’s own description gives a sense of scale and attrition:

Clinical trial phases (FDA description)
Phase	Typical participants	Typical length	Main purpose	Share that move on
Phase 1	20 to 100 healthy volunteers or people with the condition	Several months	Safety and dosage	About 70%
Phase 2	Up to several hundred people with the condition	Several months to 2 years	Efficacy and side effects	About 33%
Phase 3	300 to 3,000 people with the condition	1 to 4 years	Efficacy and monitoring of adverse reactions	About 25 to 30%
Phase 4	Several thousand people with the condition	After approval	Safety and efficacy in routine use	Not applicable

Recruitment status: where the study is now

Not yet recruiting: participants are not yet being recruited.
Recruiting: participants are being recruited, whether or not anyone has enrolled yet.
Enrolling by invitation: participants are being selected from a predetermined population.
Active, not recruiting: the study is continuing (participants are receiving the intervention or being examined) but no new participants are being enrolled.
Completed: the study ended normally.
Suspended: halted early but may resume.
Terminated: halted early and will not resume. Look for the stated reason; it can be safety, futility, business or enrollment.
Withdrawn: halted before the first participant was enrolled.

Sponsors are expected to update a changed status within 30 days, and to verify the whole record at least every 12 months. A record whose verification date is years old may no longer reflect reality.

The two completion dates

The primary completion date is when data collection for the primary outcome measure is complete, usually the last participant’s last visit for that endpoint. Topline results announced by companies normally follow this date. The study completion date is when data collection for secondary outcomes and safety is also complete.

Both dates can be “estimated” or “actual”. A string of estimated dates moving later is a common early sign of slow enrollment.

Design fields worth checking

Enrollment: the number of participants, marked as estimated or actual.
Allocation and masking: whether participants were randomised, and who was blinded. An open-label, single-arm study answers a different question from a randomised, double-blind one.
Arms and interventions: what each group received, including the comparator (placebo, standard of care or another drug).
Primary outcome measure: the pre-specified main endpoint and when it is measured. Compare it with what the company later highlights.
Sponsor and collaborators: who is responsible for the study and who is helping fund or run it.

The results tab and reporting deadlines

Under US law (FDAAA 801 and its rule, 42 CFR Part 11) and NIH policy, applicable clinical trials and NIH-funded trials must be registered within 21 days of enrolling the first participant, and results must be submitted no later than one year after the primary completion date, with limited exceptions. Posted results include participant flow, baseline characteristics, outcome measures and adverse events in a standard format.

A missing results tab does not by itself mean results are overdue: some studies are not covered, some deadlines have been legitimately delayed, and newly submitted results go through quality-control review before posting.

Beyond ClinicalTrials.gov

Many trials are registered elsewhere as well. The WHO International Clinical Trials Registry Platform searches across national registries, and trials authorised in the EU under the Clinical Trials Regulation are published in the EU Clinical Trials Information System (CTIS). On PharmaRadar360, the trials view collects new trial records and results announcements, and drug profiles link a molecule to its key studies.

Sources

This guide is general information for professionals, written from the official sources listed above. It is not legal, regulatory or medical advice. Rules change: confirm details with the regulator before relying on them.