Definition
A randomised controlled trial allocates participants by chance to receive either the intervention under study or a control, such as placebo or an existing standard. Randomisation balances known and unknown confounding factors between groups, so differences in outcome can be attributed to the intervention. Blinding participants, investigators and assessors further reduces bias. Trials are prospectively registered, for example on ClinicalTrials.gov, with prespecified primary outcomes and analysis plans, and are reported under the CONSORT guidelines. RCTs sit near the top of the evidence hierarchy, below systematic reviews of RCTs. Most research peptides sold for laboratory use have no published RCTs, which is important context when reading claims about them.