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How to read a study

Studies come in many forms, from the laboratory to large studies in humans. Here are six questions that help you understand what a study about peptides tells you.

Written by The Peptideguiden editors. Last updated 29 October 2026. 2 min.

Contents
  1. 1. Was the study done in humans, animals or cells?
  2. 2. Was the study randomised and controlled?
  3. 3. How many took part?
  4. 4. Who paid for the study?
  5. 5. What was actually measured?
  6. 6. Are the results published?
  7. How we assess the evidence
  8. Questions and answers
  9. Sources
Researchers work with samples and notes in a laboratory

In short

  • First check whether the study was done in humans, animals or cells.
  • Randomised studies with placebo give the most reliable answers.
  • Large studies give the most certain answers.
  • Look at who paid for the study, and what was actually measured.

1. Was the study done in humans, animals or cells?

This is the first question. Results in animals and cells are the starting point for all research on new medicines, and promising findings there lead on to studies in humans.[1]

For BPC-157, for example, there are many animal studies, and the first studies in humans have been done.[2]

2. Was the study randomised and controlled?

In a randomised controlled trial (RCT), chance decides who gets the substance and who gets placebo, a dummy treatment. Then the difference between the groups can be put down to the substance. If the study is also double-blind, neither the participants nor the researchers know who gets what.

A control group makes it easier to see how much of the improvement is due to the substance.

3. How many took part?

The more participants, the more certain the result. The largest study of retatrutide had 2,339 participants.[3] The first studies of a new substance are often much smaller.

Small studies are a good first step. Larger studies give more certain answers, which is why we always show how many took part.

4. Who paid for the study?

Most large medicine studies are paid for by the company developing the medicine. We give the funding in the source lists where it is known.

5. What was actually measured?

Look at what the researchers measured. The studies of CJC-1295, for example, measured the level of growth hormone in the blood.[4] The study of Semax in healthy adults measured brain activity with MRI.[5]

6. Are the results published?

Many studies are registered before they start, and the results are published when they are ready. On the peptide pages, we say when a study is registered but its results are not published yet.

How we assess the evidence

The research stage is shown for each use on the peptide pages.

Questions and answers

What is the difference between a review and a systematic review?

A systematic review searches for all studies on a question using a fixed method. A narrative review is an expert’s overview of the field, and gives a good summary and useful background.

What does placebo mean?

Placebo is a dummy treatment, for example salt water, that looks like the real substance. It is used to see whether an effect comes from the substance or from expectations.

Why does research start with animal studies?

Because they show how a substance works, and whether it is worth testing further in humans. Promising animal studies are the basis for studies in humans.

Sources

  1. [1]

    Mak IW, Evaniew N, Ghert M. Lost in translation: animal models and clinical trials in cancer treatment. Am J Transl Res. 2014.

    PMID 24489990Review

  2. [2]

    Vasireddi N, Hahamyan H, Salata MJ, et al. Emerging Use of BPC-157 in Orthopaedic Sports Medicine: A Systematic Review. HSS J. 2025.

    PMID 40756949DOIMeta-analysis

  3. [3]

    Jastreboff AM, Kaplan LM, Davies MJ, et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity. N Engl J Med. 2026.

    PMID 42814954DOIRCT · n = 2,339 · Funding or ties: Eli Lilly.

  4. [4]

    Teichman SL, et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. J Clin Endocrinol Metab. 2006.

    PMID 16352683DOIRCT

  5. [5]

    Lebedeva IS, Panikratova YR, Sokolov OY, et al. Effects of Semax on the Default Mode Network of the Brain. Bull Exp Biol Med. 2018.

    PMID 30225715DOIControlled study · n = 24