GlossaryStacking & CyclingStack
Stacking & Cycling

Stack

Also known as: protocol stack · peptide stack

A stack is two or more compounds used during the same period, usually chosen because they are thought to act through different mechanisms on the same goal.

A stack is the set of compounds you run at the same time. Stacks are usually built on the idea of complementary mechanisms: two compounds that reach the same outcome through different receptors or pathways might add up to more than either one alone. "Stack" is community vocabulary, not a clinical or regulatory term, and most stacks discussed online have never been tested as a combination.

There are real examples of combinations studied properly. In a 1990 study in 18 healthy men, a synthetic growth hormone-releasing peptide (GHRP) given together with growth hormone-releasing hormone (GHRH) released growth hormone synergistically at submaximal GHRP doses, which supported the idea that the two act through separate mechanisms. That was a single-injection study measuring a hormone peak, not an outcome trial. A much larger example is cagrilintide plus semaglutide: a 68-week phase 3 trial randomized 3,417 adults to the combination, either drug alone, or placebo, and reported a mean body-weight change of −20.4% with the combination versus −3.0% with placebo.

Why it matters

Every compound you add brings its own side effects, and some of them overlap. In that same combination trial, gastrointestinal adverse events affected 79.6% of people on the combination and 39.9% of people on placebo. A stack also makes it harder to know what is doing what: if you start two compounds on the same day and something changes, good or bad, you cannot attribute it to either one.

Evidence for a stack is only as good as the evidence for the combination itself. A popular pairing like BPC-157 with TB-500 rests on preclinical data for each compound separately. A 2025 systematic review of BPC-157 in orthopedic sports medicine included 35 preclinical studies and a single retrospective human study, so there is no controlled human evidence for BPC-157 on its own, let alone combined with TB-500.

How to evaluate a stack

  1. Write down the proposed mechanism of each compound and the outcome you expect it to affect. If two compounds act on the same receptor, you are adding overlap, not a second mechanism.
  2. Check whether the combination itself has been studied, not just each compound separately, and note what kind of study it was: cell, animal, single dose, or randomized trial.
  3. List the side effects each compound is known for and mark the ones they share. DoseCraft's interaction checker (/tools/interaction-checker) flags some known overlapping pairs, such as two GLP-1 agonists together.
  4. Start compounds one at a time, far enough apart that you can see each one's effect, rather than all on day one.
  5. Log every dose and every change so you can tell which compound a change followed.

Common mistakes

  • Treating synergy in a single-injection hormone study as proof of better long-term results.
  • Starting every compound in the stack on the same day, so no change can be traced to any one of them.
  • Combining two compounds that act on the same receptor and expecting double the effect rather than more side effects.
  • Assuming a stack is evidence-based because each ingredient has some studies behind it on its own.
  • Changing the doses of several compounds at once when something goes wrong.

Sources

  1. Clinical trialGrowth hormone (GH)-releasing peptide stimulates GH release in normal men and acts synergistically with GH-releasing hormone. J Clin Endocrinol Metab, 1990. PMID 2108187.
  2. Clinical trialCoadministered Cagrilintide and Semaglutide in Adults with Overweight or Obesity. N Engl J Med, 2025. PMID 40544433.
  3. Systematic reviewEmerging Use of BPC-157 in Orthopaedic Sports Medicine: A Systematic Review. HSS J, 2025. PMID 40756949.

Page updated . How we grade evidence: methodology.

Related Terms

Cycle

A cycle is a planned period of taking a compound followed by a planned break, often repeated over time.

Receptor Desensitization

Receptor desensitization is the drop in a cell's response to a drug or hormone after repeated or continuous stimulation of its receptor.

GHRH Analog

A GHRH analog is a modified growth hormone-releasing hormone that activates the GHRH receptor on the pituitary to release the body's own growth hormone.

Growth Hormone Secretagogue

A growth hormone secretagogue (GHS) is a compound that makes the pituitary release its own growth hormone, usually by activating the ghrelin receptor.

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