--- title: "From cell dish to clinic: study types" url: https://humanpeptides.fyi/knowledge-base/study-types site: humanpeptides.fyi last_reviewed: 2026-10-12 --- # From cell dish to clinic: study types The index labels every one of its 48 entries by evidence strength. The kind of study behind a claim is a large part of that label. Below, the study types the index cites, in order from work outside a living organism to studies that combine human trials, each with its glossary definition. - [Evidence labels explained](https://humanpeptides.fyi/knowledge-base/evidence-labels) - [Method](https://humanpeptides.fyi/method) ## The ladder ### 1. In vitro Studied in cells or tissue in a dish or test tube, outside a living organism. 3 of 48 compounds mention "in vitro" in their evidence text. [In vitro in the glossary](https://humanpeptides.fyi/glossary#in-vitro) ### 2. Ex vivo Studied in tissue taken from a living organism and kept alive outside it, such as isolated hair follicles. 1 of 48 compounds mention "ex vivo" in their evidence text. [Ex vivo in the glossary](https://humanpeptides.fyi/glossary#ex-vivo) ### 3. In vivo / animal study Studied in a living organism, most often mice or rats. Results frequently fail to carry over to humans. 21 of 48 compounds mention "animal" in their evidence text. [In vivo / animal study in the glossary](https://humanpeptides.fyi/glossary#in-vivo) ### 4. Preclinical Research done before human testing, in cells and animals. 1 of 48 compounds mention "preclinical" in their evidence text. [Preclinical in the glossary](https://humanpeptides.fyi/glossary#preclinical) ### 5. Case report A description of what happened to one patient or a few patients. Useful for spotting rare effects, not for judging how often they occur. 2 of 48 compounds mention "case report" in their evidence text. [Case report in the glossary](https://humanpeptides.fyi/glossary#case-report) ### 6. Pilot study A small early study meant to test feasibility, not to prove an effect. 1 of 48 compounds mention "pilot" in their evidence text. [Pilot study in the glossary](https://humanpeptides.fyi/glossary#pilot) ### 7. Observational study / cohort A study that follows people without assigning a treatment. It can show associations but not cause and effect. 1 of 48 compounds mention "observational" in their evidence text. [Observational study / cohort in the glossary](https://humanpeptides.fyi/glossary#observational) ### 8. Randomized controlled trial (RCT) A study that assigns people by chance to the treatment or a comparison (often placebo), so differences in outcome can be attributed to the treatment rather than to who chose it. 16 of 48 compounds mention "rct" in their evidence text. [Randomized controlled trial (RCT) in the glossary](https://humanpeptides.fyi/glossary#rct) ### 9. Double-blind Neither participants nor investigators know who received the treatment until the study ends, which reduces bias in reporting and assessment. 0 of 48 compounds mention "double-blind" in their evidence text. [Double-blind in the glossary](https://humanpeptides.fyi/glossary#double-blind) ### 10. Meta-analysis A study that statistically combines the results of several earlier studies on the same question. 0 of 48 compounds mention "meta-analysis" in their evidence text. [Meta-analysis in the glossary](https://humanpeptides.fyi/glossary#meta-analysis) ## Related terms ### Retrospective study A study that looks back at existing records rather than following people forward under a plan. [Retrospective study in the glossary](https://humanpeptides.fyi/glossary#retrospective) ### Placebo-controlled A study in which the comparison group receives an inactive look-alike, so that expectation effects are present in both groups. [Placebo-controlled in the glossary](https://humanpeptides.fyi/glossary#placebo-controlled) ### Open-label / unblinded Everyone knows who received the treatment. Results are more prone to expectation and reporting bias. [Open-label / unblinded in the glossary](https://humanpeptides.fyi/glossary#open-label) ### Phase 1, 2 and 3 trials Phase 1 tests safety and dosing in a small group; phase 2 looks for signs of effect in more people; phase 3 tests effect and safety at scale and usually supports an approval application. [Phase 1, 2 and 3 trials in the glossary](https://humanpeptides.fyi/glossary#phase) ### Anecdotal A personal report, for example a forum post. Unverified, not controlled, and not evidence that something works or is safe. 26 of 48 compounds mention "anecdotal" in their evidence text. [Anecdotal in the glossary](https://humanpeptides.fyi/glossary#anecdotal) ## Where to read more - [Evidence labels explained](https://humanpeptides.fyi/knowledge-base/evidence-labels) - [How evidence labels are assigned](https://humanpeptides.fyi/method#evidence-tiers) - [Glossary](https://humanpeptides.fyi/glossary) > humanpeptides.fyi makes no claims of its own. Every benefit, side effect, nickname and quote reports what a cited source says, with its link. Not medical advice.