What happens when you stack them?
Choose up to six peptides or drugs. The analyzer checks them against interactions recorded from FDA labels and published studies, a label rule against combining GLP-1 drugs, recorded effects on blood sugar and blood pressure, WADA status, and the evidence grade of each one, and it lists what has never been checked. Every flag shows where it comes from. It reports what is recorded; it cannot tell you a combination is safe, and it is not a substitute for a prescriber or pharmacist.
348 compounds; 87 with interactions recorded from a label or study. Related: the interaction matrix, the interaction checker and serious reactions to injected peptides.
What the analyzer checks
People rarely use one peptide. Clinics sell protocols, sellers sell blends, and forums trade 'stacks' of three, four or six compounds. The questions are always the same: do any of these interact, do any of them do the same thing twice, and is any of it banned in my sport? The Stack Safety Analyzer answers those questions with sources, and only with sources. Choose up to six compounds from the encyclopedia and it checks them five ways.
First, label rules: the prescribing information for Wegovy and Zepbound both say the drug should not be combined with another GLP-1 receptor agonist 1 2, so any stack containing two GLP-1 drugs is flagged with those quotations. Second, recorded interactions: our interaction matrix holds interactions taken from FDA labels or human studies for 87 compounds, and the analyzer flags any recorded interaction that names another compound on your list, by name, alias or class. Third, shared concerns: components whose recorded interactions affect blood sugar or blood pressure are tallied together. Fourth, sport: anything on WADA's 2026 Prohibited List is named. Fifth, gaps: anything never reviewed, or reviewed with nothing found, is listed rather than hidden.
Where the flags come from
The analyzer has no opinions of its own. Its interaction data is the same interaction matrix the site publishes: 57 compounds whose FDA label lists interactions, cited to the label version; 30 with at least one human interaction study, cited by PubMed ID; and 109 where a recorded PubMed search found no human interaction study. The text of each flag is the matrix's own wording, and each carries its citation underneath.
Class matching is deliberately narrow. A label that warns about 'other diabetes drugs' or 'insulin' is matched to GLP-1 drugs and insulins on your list, because those labels mean exactly that; a warning about 'oral medications' or 'drugs metabolised by cytochrome P450 enzymes' is shown in the component's record but is not matched to anything, because no entry's data says which peptides fall into those groups. The GLP-1 rule applies to entries whose class description names them as GLP-1 receptor agonists, and the build checks that the label sentences it quotes are still in the labels we hold.
Reading the results
Red-edged flags are the strongest: a label saying a combination is not recommended, or a WADA prohibition. Amber flags are recorded interactions between components, and gaps in what has been checked. Blue flags are information: two components with recorded effects on the same thing, such as blood sugar, or two entries described as acting on the same receptor. A shared target is not proof of a problem, and the analyzer says so; it is a reason to ask whether the combination adds anything, or adds risk.
The component table at the end gives each compound's regulatory status, evidence grade and interaction record. A stack of compounds graded 'low', with interaction records that read 'unreviewed', is a stack nobody has studied, whatever else the analyzer finds.
Why 'no flags' is not 'safe'
The most common result for research-peptide stacks is no recorded interaction at all, and it is the most misleading one if read carelessly. 91 encyclopedia entries have never been reviewed for interactions, and most research peptides that have been reviewed are in the 'none found' group: a search for human interaction studies returned nothing. Nothing found means nothing was looked for in people, not that nothing happens. The analyzer prints that distinction for every component, and our article on serious reactions to injected peptides shows how a multi-peptide injection can go wrong in ways no one can trace afterwards.
Combining compounds also makes side effects impossible to attribute. If something goes wrong on a six-peptide stack, there is no way to tell which component, or which combination, caused it, and for most research peptides FDA says it has little or no human safety information about any of them alone.
Stacks and blends
A stack can be separate vials or one blended vial. If it is a blend, every draw delivers every component in a fixed ratio, so you cannot reduce one without reducing all of them. The Blend Calculator works out what each draw contains, and our article on blend dose maths explains why no blend has an evidence-based dose. Use the analyzer to see what is known about the combination, and the calculator to see what is in the syringe.
Sources
- Novo Nordisk. Wegovy (semaglutide) US prescribing information, Limitations of Use (DailyMed set ee06186f, effective June 18, 2026); read October 3, 2026.
- Eli Lilly. Zepbound (tirzepatide) US prescribing information, Limitations of Use (DailyMed set 487cd7e7, effective August 28, 2026); read October 3, 2026.
This explainer describes how the tool works and what its numbers rest on. It is not medical advice and does not recommend any dose or product.