Research information only. PrecisePep is an educational library. It is not medical advice and is not intended to assist, encourage or enable self-administration. The compounds documented here are research chemicals — most are not approved for human use. Read the full disclaimer.
PrecisePep/Peptide Library/Insulin & analogues
Metabolic & Adipose Regulation
human insulin · insulin glargine · insulin lispro · insulin aspart · insulin degludec
The foundational peptide therapy, and the only compound in this library that reliably kills people through ordinary dosing error. It is here for completeness and for one specific warning.
Insulin is a 51-residue peptide hormone and the oldest peptide therapy in clinical use. In type 2 diabetes it is not a first-line agent but a later one — added when beta-cell function has declined far enough that oral agents and incretin therapy no longer maintain glycaemic control. It works by directly driving cellular glucose uptake and suppressing hepatic glucose output, and it does so regardless of how much endogenous beta-cell function remains. That is what makes it effective and what makes it dangerous.
Modern practice uses engineered analogues rather than human insulin: long-acting basal analogues (glargine, detemir, degludec) that provide flat background coverage, and rapid-acting prandial analogues (lispro, aspart, glulisine) that cover meals. The engineering changes the absorption profile, not the mechanism.
This page exists for two reasons. Insulin belongs in a peptide library on the merits — it is the peptide therapy everything else is measured against. And people do source it outside the prescription system, driven by cost, which is the single most dangerous thing documented anywhere on this site.
This site documents grey-market and community dosing for every other compound in the library, on the view that studying what people actually do is more useful than pretending they do something else. It does not do that for insulin.
The reason is specific rather than squeamish. For every other compound here, a dosing error produces an unknown or a wasted month. For insulin, a dosing error produces severe hypoglycaemia — confusion, seizure, coma, death — over hours, in someone who may be asleep and alone. There is no self-titration heuristic that makes that safe without glucose monitoring and clinical support, and publishing numbers would imply otherwise. The clinical principles are described below; the numbers are not.
Insulin receptor agonism. Binding the insulin receptor triggers autophosphorylation and IRS/PI3K/Akt signalling, driving GLUT4 translocation to the cell membrane in muscle and adipose tissue — the step that moves glucose out of the blood and into cells.
Suppression of hepatic glucose output. Insulin restrains gluconeogenesis and glycogenolysis in the liver. In type 2 diabetes, inappropriate hepatic glucose production is a major driver of fasting hyperglycaemia, and basal insulin targets it directly.
Anabolic and antilipolytic effects. Insulin promotes protein synthesis, inhibits lipolysis and drives lipogenesis. This is why insulin therapy typically causes weight gain, and why supraphysiological insulin outside a diabetic context promotes fat storage.
Analogue engineering. Basal analogues use isoelectric precipitation (glargine), fatty-acid acylation (detemir, degludec) or multihexamer formation to slow absorption to a flat 24-hour or longer profile. Rapid analogues use amino-acid substitutions that reduce hexamer stability so the peptide dissociates and absorbs faster. Same receptor, different arrival times.
Why the therapeutic window is narrow. There is no glucose-dependence. Unlike incretin agonists, which amplify insulin secretion only when glucose is elevated, exogenous insulin lowers glucose whether or not it needs lowering. A dose appropriate for a meal that is then not eaten is an overdose.
Effects that have been reported. A study-tier entry means a result was published — not that the effect is established, reproducible, or transferable from a rodent to a person.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
The defining property. Where oral agents and incretins depend on remaining pancreatic function, insulin does not — which is why it remains effective at every stage of type 2 diabetes.
In continuous clinical use since 1922, with the most extensive real-world evidence base of any compound documented on this site by a wide margin.
Sustained glycaemic control reduces retinopathy, nephropathy and neuropathy progression — established across landmark trials including UKPDS in type 2 diabetes.
Flatter, more predictable absorption profiles reduce overnight hypoglycaemia relative to older intermediate-acting human insulin — a genuine advance rather than a marketing one.
Trials of basal insulin have demonstrated cardiovascular safety rather than benefit — a meaningful distinction from the GLP-1 class, several of which reduce events.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
Short-course intensive insulin at diagnosis has been studied for inducing remission and preserving beta-cell function, with genuinely interesting results. A clinical strategy decision, not a self-directed one.
Insulin is used in bodybuilding for its anabolic and nutrient-partitioning effects. This is the single most lethal practice documented anywhere on this site and has an established record of fatalities. It is named here so that it is not mistaken for an omission.
Insulin promotes lipogenesis and inhibits lipolysis, so weight gain is expected and works against the underlying insulin resistance — one reason incretin agents are now preferred earlier in the sequence.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
Insulin rationing, splitting doses to stretch supply, and informal sharing are real, documented phenomena driven by cost rather than by experimentation. Rationing insulin causes diabetic ketoacidosis and has killed people. If cost is the problem, the routes below are the answer, not rationing.
Mistaking a rapid-acting analogue for a basal one, or a U-100 for a U-500 concentration, is a recognised and recurring cause of severe hypoglycaemia — including in clinical settings.
A relevant crossover for this site: the U-100 syringes used throughout the peptide community are insulin syringes, and their unit markings are calibrated for insulin. Every other compound in this library borrows that hardware.
Adverse effects, contraindications and unknowns. The grey-market tier is where under-reporting is worst: uncontrolled use produces no systematic safety surveillance at all, so absence of a reported harm is not evidence of safety.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
The dominant risk and the reason this page is written differently from the others. Progresses through sweating, tremor and confusion to seizure, coma and death. Onset can be within an hour for rapid analogues, and it is most dangerous overnight when symptoms go unnoticed.
Repeated hypoglycaemia blunts the counter-regulatory warning symptoms, so subsequent episodes arrive without warning. The risk compounds rather than staying constant.
Expected and mechanistically inevitable given the antilipolytic and lipogenic effects.
Insulin drives potassium intracellularly. Clinically significant in overdose and in acute settings, and a route to cardiac arrhythmia independent of the glucose effect.
Repeated injection into the same site produces fatty tissue changes that then alter absorption unpredictably — a common and under-recognised cause of erratic glucose control.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
Insulin overdose is a recognised method of self-harm and of homicide, and is difficult to detect retrospectively. This is not a peptide-community concern in the ordinary sense, and it is part of why insulin supply is controlled.
GLP-1 agonists, sulfonylureas, alcohol and exercise all lower glucose. Every one of them requires insulin dose reduction, and adding an incretin agonist to insulin without reducing it is a specific and common route to severe hypoglycaemia.
Insulin degrades with heat and freezing. Product obtained outside the regulated supply chain has an unknown temperature history, and degraded insulin produces unpredictable and under-effective dosing.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
The most feared complication among people who use insulin, and the reason continuous glucose monitoring with alarms has changed the safety picture so substantially.
Widely reported and entirely rational for a drug where a decimal place matters.
Figures below are documented, not recommended. Study ranges come from published protocols in the stated model; grey-market ranges are what the research community reports using and carry no safety validation of any kind.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
Insulin therapy in type 2 diabetes typically begins with a weight-based basal dose, titrated against fasting glucose over days to weeks, with prandial insulin added later if postprandial control remains inadequate. Titration is driven by measured glucose, not by a schedule. Specific figures are deliberately not reproduced on this page — see the note in the overview.
Insulin is dosed in international units. U-100 means 100 units per millilitre. This is the only compound in the library where the syringe unit markings correspond directly to the dose rather than requiring a concentration calculation.
Adding a GLP-1 agonist, pramlintide or a sulfonylurea to established insulin requires reducing the insulin dose. Pramlintide carries a boxed warning to this effect and typically requires halving prandial insulin at initiation.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
CGM with hypoglycaemia alarms is the single most meaningful safety advance for insulin users in decades, and availability has broadened considerably. Anyone using insulin without glucose monitoring is flying blind on the one variable that matters.
See the note below. Rationing is more dangerous than any of them.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
This site reproduces community dosing for every other compound in the library. It does not for insulin. The reasoning is set out in the overview, and it is a deliberate editorial position rather than a gap.
Insulin rationing causes diabetic ketoacidosis and has killed people. These routes exist and are worth exhausting first:
None of these require sourcing insulin outside the regulated supply chain, where potency and cold-chain history are unknown.
Combination effects. Almost no peptide combination has been studied as a combination in humans; stack logic is overwhelmingly mechanistic inference and community practice. Each linked compound has its own page.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
An established and well-studied combination in type 2 diabetes, available as fixed-ratio products. It improves control while limiting insulin dose escalation and weight gain — but requires insulin dose reduction at initiation.
Pramlintide is approved specifically as a mealtime adjunct to insulin, restoring the amylin arm of the beta-cell response. It carries a boxed warning for severe insulin-induced hypoglycaemia.
Standard practice — metformin is generally continued when insulin is added, reducing the insulin dose required.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
GLP-1 agonists, amylin analogues, sulfonylureas, alcohol, exercise and reduced intake all lower glucose. Each requires the insulin dose to be reconsidered, and this is where most severe hypoglycaemia in the real world comes from.
IGF-1 has appreciable insulin-receptor cross-reactivity. Combining an unbuffered IGF-1 analogue with insulin is the most acutely dangerous pairing that could be assembled from this library.
Growth hormone is counter-regulatory to insulin, so an effective GH stack can increase insulin needs — a change that will show up as deteriorating control rather than as an obvious adverse event.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
A recurring and specific error, and one this library is more likely than most to encounter given how widely GLP-1 agonists are sourced outside the prescription system.
Whole schedules — dosing, titration, cycle length, and off-time — as documented in trials, as proposed from mechanism, and as circulated in the research community. Reproduced for study and comparison only.
Highest confidenceReported in peer-reviewed literature, registered clinical trials, or regulatory filings. Note the model: much peptide literature is in vitro or rodent work, not human trial data.
Standard clinical protocols specify weight-based starting doses titrated against fasting glucose, with defined escalation intervals and hypoglycaemia stopping rules. These live in clinical guidelines and are implemented with monitoring and clinician contact.
More intensive regimens match prandial insulin to carbohydrate intake using individualised ratios and correction factors, requiring structured education programmes to use safely.
Unproven — inference onlyExtrapolated from a known mechanism, receptor profile, or adjacent compound class. Biologically plausible but not directly demonstrated for this compound in this context.
Every insulin regimen is titrated against measured glucose. Without monitoring there is no protocol, only a guess with a narrow margin.
Uncontrolled reportsAggregated from research-community logs, forums, vendor literature and self-reported experience. Uncontrolled, unverified, subject to placebo, polypharmacy and product-purity confounds. Lowest evidentiary weight.
As with dosing, community insulin protocols are deliberately not reproduced on this site.
This page publishes no dosing, and this section is not an exception to that. What it covers is the thing that actually kills people with insulin-treated diabetes outside hospital — which is not the disease, and is not usually the drug.
Insulin is the oldest peptide drug there is, and the only one in this library where a dosing error is measured in hours rather than months. This site documents grey-market and community dosing for every other compound in the library. It does not do that for insulin, and this section does not either.
Pathophysiology
The brain has no meaningful glucose stores and depends on continuous supply. Severe hypoglycaemia causes confusion, seizure, coma and death, and it does so over minutes to hours rather than over years.
Mechanistic rationale
Every other risk associated with insulin is slow. This one is fast. Anything that increases insulin sensitivity or reduces carbohydrate intake without a corresponding dose reduction moves someone toward it — which includes exercise, alcohol, illness, weight loss, and starting a GLP-1 agonist, an amylin analogue or an SGLT2 inhibitor. Impaired awareness of hypoglycaemia develops with repeated episodes and removes the warning symptoms entirely.
Community reports
Community discussion of adding compounds to an insulin regimen rarely addresses dose reduction of the insulin, which is where the danger sits.
Components carrying the argument: The mechanism working as intended, in excess
Pathophysiology
Type 1 diabetes is universally fatal without insulin. Untreated, diabetic ketoacidosis develops over hours to days.
Mechanistic rationale
Insulin rationing — taking less than prescribed to make a vial last — is documented, common where insulin is expensive, and it kills people. This is the reason the compound is in this library at all: if cost is the problem, there are legitimate routes that do not involve buying an unverified vial. Manufacturer price caps, patient assistance programmes, community health centres, and older human insulins available over the counter in some jurisdictions at a fraction of analogue prices. Those routes are listed in the dosing section of this page.
Community reports
People seek unlicensed insulin overwhelmingly on cost grounds rather than for enhancement. That is a solvable problem and it is solvable without the vial.
Components carrying the argument: Not pharmacology — access
Pathophysiology
Insulin is anabolic, which is the basis for its use in physique contexts. It is also the most direct route to severe hypoglycaemia available.
Mechanistic rationale
Deaths in this context are documented and are not rare relative to the size of the population using it. The mechanism is simple: an anabolic dose in someone with normal pancreatic function has no counter-regulatory margin, and unconsciousness can arrive before the person can eat. There is no version of this that this site will publish figures for.
Community reports
Discussed openly, usually with confident protocols and no mention of what happens when one is followed while asleep.
Components carrying the argument: Anabolic effect, no margin
Pathophysiology
Type 2 diabetes is progressive, and beta-cell function declines over time such that many people eventually need insulin.
Mechanistic rationale
Insulin used to be added earlier than it now is. GLP-1 agonists, SGLT2 inhibitors and dual agonists have shifted the sequence, partly because they lower glucose without hypoglycaemia and partly because they carry cardiovascular and renal outcome data insulin does not. Insulin remains essential when it is needed — the change is in when that point arrives.
Community reports
Adding a GLP-1 agonist to insulin is common and correct clinically, and requires the insulin dose to come down. That reduction is the part that gets skipped.
Components carrying the argument: Glucose lowering without a ceiling
| Question | Position |
|---|---|
| Dosing published here? | No — and this section is not an exception |
| Fastest serious risk | Severe hypoglycaemia — minutes to hours |
| What raises that risk | Exercise, alcohol, illness, weight loss, GLP-1s, amylin, SGLT2 |
| Why people buy it unlicensed | Overwhelmingly cost |
| Legitimate routes | Price caps, assistance programmes, FQHCs, OTC human insulin |
| Bodybuilding use | Documented deaths; no protocol here |
Insulin-treated diabetes is managed with a clinical team. Structured education programmes — DAFNE and equivalents — improve control and reduce severe hypoglycaemia. Continuous glucose monitoring has transformed safety and is increasingly standard. Hypoglycaemia awareness should be assessed, because losing it is both dangerous and reversible with careful avoidance of lows.
If cost is the barrier, that is a problem with solutions, and the landscape has improved. In the United States, Medicare Part D caps insulin at $35 per month per product. Around thirty states have enacted their own caps for state-regulated commercial plans, and Eli Lilly, Novo Nordisk and Sanofi have all voluntarily extended $35 caps to many commercial plans and to uninsured patients. There is still no federal cap covering all commercially insured people — a bipartisan bill reintroduced in 2026 would extend it from 2027, and it has not passed. Alongside those: patient assistance programmes, federally qualified health centres, and older human insulins available at a fraction of analogue cost. A prescriber or pharmacist can navigate all of it, and every route is safer than an unverified vial.
Physical-chemistry reference for laboratory handling of the lyophilised material. Reproduced so that stability and concentration mathematics can be studied — see the calculator for the arithmetic and the reconstitution guide for sterile technique.
Insulin is supplied as a ready-to-use solution or suspension in vials, pens and cartridges. It is not reconstituted from lyophilised powder, and it is not dosed in milligrams — which is why it does not appear in this site’s calculator. Adding it would invite exactly the unit confusion that causes harm.
Unopened: refrigerated 2–8 °C until the expiry date. In use: room temperature for a defined period that varies by product, typically 28 days. Never freeze — frozen insulin is discarded, not thawed. Heat exposure degrades potency without visible change.
Vials, pre-filled pens and pump cartridges. U-100 is standard; U-200, U-300 and U-500 concentrations exist and are a recognised source of dosing error.
Cloudy appearance in a product that should be clear, or clumping and frosting in a suspension, indicates degradation. Product obtained outside the regulated supply chain has an unknown temperature history, and degraded insulin under-doses unpredictably.
Regulatory status changes and differs by country. This is a summary for orientation, not legal advice — check your own jurisdiction.
Approved and foundational. Insulin has been in clinical use since 1922 and is on the WHO Model List of Essential Medicines. It is a prescription medicine in most jurisdictions, though regular and NPH human insulin are available without prescription in many US states.
It is not a research chemical and is not sold by the research-peptide suppliers documented elsewhere on this site. It appears here because it is the foundational peptide therapy and because cost-driven informal sourcing is a real and dangerous phenomenon.
Regulatory and trial claims re-checked against primary sources on 16 August 2026. Checked: Medicare and state $35 caps, manufacturer programmes, pending federal bill. Approvals, trial readouts and compounding decisions move faster than anything else on this page — a date here means someone looked, not that nothing has changed since.
Insulin is explicitly prohibited by WADA under S4 (hormone and metabolic modulators) at all times, in and out of competition, except where a therapeutic use exemption is in place for insulin-requiring diabetes.
Links resolve to PubMed records, trial registries, publisher pages or primary documents. Where a body of work rather than a single paper is cited, the link opens a PubMed query so the full result set — including newer papers than this page — can be reviewed. Verify every claim against the primary source before relying on it.
For educational and research reference only. Nothing on this site is medical advice, a recommendation, or an instruction to administer any substance to a human being. Every figure on this page is a record of what has been reported, not a recommendation. Full disclaimer.
