What people ask — and how we answer

A peptide is a chain of multiple amino acids — shorter than a protein. The boundary is fuzzy, but typically up to about 50 amino acids is called a peptide, above that a protein. Peptides occur endogenously (e.g. hormones like insulin or oxytocin) and are synthetically produced to mimic, enhance or study these actions.

Both consist of amino-acid chains. Peptides are shorter (commonly up to ~50 amino acids) and often lack pronounced 3D folding. Proteins are longer, fold into complex structures and thereby gain specific functions like enzymatic activity. The threshold is conventional, not biochemically hard — what matters more is whether the structure is independently functional.

Half-life (t½) is the time for an active substance's concentration in the body to fall to half. After 4–5 half-lives, around 94–97% is eliminated. This is a simplified model — real pharmacokinetics can be multi-phasic with different half-lives in plasma and tissues. When dosed repeatedly at intervals shorter than the half-life, the substance accumulates to a steady state.

Bioavailability is the proportion of an administered substance that reaches systemic circulation unchanged. A subcutaneous injection bypasses gastric acid and the liver's first-pass effect, which is why many peptides have high subcutaneous bioavailability (typically 70–95%). Oral administration is different — peptides are rapidly broken down in the digestive tract, so oral bioavailability is often in the single-digit percentage range. Rybelsus (oral semaglutide) uses an absorption enhancer (SNAC) to reach clinically relevant levels at all.

RCT stands for Randomised Controlled Trial. Participants are randomly allocated to treatment and control groups, ideally blinded. Randomisation reduces systematic bias, blinding minimises expectation effects. RCTs are considered the methodologically strongest form of clinical evidence for "does this substance work?" — when they are large enough, well conducted and independently funded. An RCT with 12 people is methodologically an RCT but statistically questionable.

Animals differ from humans across many dimensions: metabolism, genetics, immune system, organ size, lifespan, behaviour. A mouse ages in two years, a human in 80. Doses are usually converted in mg/kg — but this regularly overestimates effects in humans or underestimates adverse events. Historically, around 90% of substances that work in animal studies turn out to be not effective enough or too toxic in clinical development. Animal models are an important first step, not proof.

In vitro literally means "in glass" — experiments outside a living organism, usually in cell culture or a test tube. In vivo means "in the living" — in a whole organism, animal or human. In-vitro results show that a substance can in principle do something; in vivo shows whether it also happens in a body's complex system. Many in-vitro effects disappear in vivo because absorption, distribution, breakdown and competition with endogenous factors come into play.

p < 0.05 means: if the null hypothesis is true (no real effect exists), the observed result or a more extreme one would be expected by chance less than 5% of the time. This is NOT the probability that the hypothesis is true. This is NOT the effect size. A tiny, clinically meaningless difference can be "statistically significant" if the sample is just large enough. Conversely, a large effect can have p > 0.05 if the sample is small. Effect size + confidence interval are the more informative quantities.

Statistical significance says: the observed result is unlikely to have arisen by chance alone. Effect size says: how large is the difference actually. These are different questions. A tiny, clinically irrelevant difference can be statistically significant if the sample is large enough (e.g. 100,000 participants). A clinically meaningful effect can appear non-significant if the sample is too small. Informative studies report both: effect size with confidence interval PLUS p-value. Reading only "significant" misses half the information.

A 95% confidence interval is a range around the estimated effect size that, in repeated similar studies, would contain the true value 95% of the time. A narrow CI means: the estimate is precise. A wide CI means: high uncertainty. Example: HR 0.80, 95% CI 0.72–0.90 means — the estimated effect is a 20% reduction, and the true effect most likely lies between 10% and 28% reduction. The CI is more informative than the p-value because it expresses effect size AND precision in one number. If the CI includes 1.0 (for hazard ratios) or 0 (for differences), the effect is not statistically significant.

Under repeated dosing at intervals shorter than the half-life, a substance accumulates in the body — the concentration after each dose is higher than after the previous one. After roughly 4–5 half-lives, the system reaches steady state: input and elimination are in equilibrium, concentration only fluctuates around a mean. For semaglutide (t½ ≈ 7 days) this takes about 4–5 weeks. Before steady state, trough and peak levels are lower than later — this explains why some effects only become visible after weeks.

Off-label use is the use of an approved medicinal product outside its approved indication, dose or patient population. Example: semaglutide is approved as Ozempic for type-2 diabetes — whoever receives it without diabetes for weight loss is in off-label use (unless it is prescribed as Wegovy with an obesity indication). Off-label is not illegal, but responsibility shifts from manufacturer to the prescribing professional. Insurance and liability issues become more complex.

AMG = Arzneimittelgesetz (German Medicinal Products Act). Governs what counts as a medicinal product, who may produce, distribute and prescribe it, and what authorisation is required. HWG = Heilmittelwerbegesetz (German Therapeutic Products Advertising Act). Governs how medicinal products and therapeutic treatments may be communicated — advertising with healing claims, indications and comparisons is heavily restricted. Both laws directly affect the discussion of non-approved peptides: "X helps with Y" is practically prohibited for non-approved substances.

Compounding is the individual preparation of a medicinal product in a pharmacy, distinct from an industrially approved finished product. In the US this is regulated under 503A/503B of the FDA compounding framework. During shortages the FDA can temporarily permit compounding — as in 2023/24 for semaglutide and tirzepatide. Compounded products are subject to less stringent controls than approved medicinal products, which can lead to risks regarding identity, purity and sterility.

The World Anti-Doping Agency (WADA) is an international organisation coordinating anti-doping rules in organised sport. It publishes the annual Prohibited List — a list of substances and methods banned in competitive sport (and partly out of competition). Federations like IOC, FIFA, UCI have signed up to the WADA Code, which makes the list a standard reference beyond sport. Many peptides appear on this list even where they are not otherwise legally restricted.

The Black Box Warning (also Boxed Warning) is the strongest warning in an FDA prescribing information. It sits in a black-bordered box at the top of the product label and flags serious, potentially life-threatening risks. Semaglutide carries a boxed warning on thyroid C-cell tumours based on rodent studies — human relevance is not established, but the FDA called for caution regardless. A boxed warning does not necessarily mean the substance is dangerous — it means the regulator explicitly wants to draw attention to a potential risk.

FDA (U.S. Food and Drug Administration) is the U.S. federal agency for food and drug safety. EMA (European Medicines Agency) is the European counterpart, based in Amsterdam. Both decide on approval, indications and safety warnings. They operate in parallel and not always in agreement — the FDA can approve an indication that the EMA rejects (or vice versa). In Germany, BfArM (Federal Institute for Drugs and Medical Devices) complements at the national level; in Switzerland, Swissmedic.

Three reasons. First: most catalogued peptides are not approved as medicinal products. A dosing recommendation for a non-approved substance falls under AMG/HWG in Germany and is simply not permitted — no matter how safe it appears. Second: the evidence often does not support it. For many peptides only animal models exist. Converting mg/kg from mouse to human is methodologically questionable — what works in animals can be ineffective or cause adverse events in humans. Third: responsibility. A dosing recommendation requires individual history, co-medication, pre-existing conditions, lab values — things only a professional in direct contact can assess. A public website cannot replace that without becoming irresponsible.

Every documented observation carries a visible evidence tier — from strong to weak: human RCT (randomised controlled trial), human trial (other human study, e.g. cohort), animal model, in-vitro (cell culture), preclinical (other preclinical), anecdotal (forum / experience reports), theoretical (only hypothesis, not established). The idea: weaker tiers are deliberately visible, not hidden. So a reader immediately sees whether a statement is "established in a 17,000-person RCT" or "frequently discussed in forums".

We aggregate structured data exclusively from open, established sources: PubMed and Europe PMC for study metadata, PubChem and ChEMBL for chemical identifiers (CAS, sequence, molecular weight), FDA / EMA / TGA / BfArM / Swissmedic for legal status, EU CosIng for cosmetic ingredients, WADA for doping status. Forums, vendor websites, influencer posts and bro-science sources NEVER enter our factual base. They can at best be explicitly marked as "anecdotal" with a clear note that no study support exists.

Unblinded self-reports are particularly prone to placebo, recall and confirmation biases. People remember positive experiences selectively, normalise neutral courses upward, and often omit adverse events. "It helped me" is not a scientific statement about efficacy — it is a statement about one person's perception. We explicitly mark such statements as "Anecdotal · Not supported by studies", because that is more honest than letting them look like evidence.