Lab math and units
Four words do most of the work in peptide lab math: mg, mcg, mL and units. The terms below explain how they connect, from the weight printed on the vial to the marks on the syringe. The site's calculator shows every step of the arithmetic for any vial and any amount of water.
- mg (milligram)
- One thousandth of a gram, a measure of weight. Peptide vials are labeled in mg, for example 5 mg, which is the amount of peptide in the vial.
- mcg (microgram)
- One thousandth of a milligram, also written µg. 1 mg equals 1,000 mcg, and charts usually give amounts in mcg, so mixing the two up makes a thousand-fold error.
- IU (international unit)
- A measure of biological activity rather than weight, defined separately for each substance against a reference standard. HCG is labeled in IU and HGH is often described in IU as well as mg, but no single factor turns IU into mg for every compound.
- mL (milliliter)
- A measure of volume, the same as 1 cc (cubic centimeter). It is the scale for the water added to a vial: 1 mL fills a 1 mL insulin syringe to the 100 mark.
- Vial size
- The amount of peptide powder in a vial, printed on the label in mg. It is a weight, not a volume, since the volume is set later by how much water is added.
- Concentration
- How much peptide is in each mL of liquid, written mg/mL. It equals the vial's mg divided by the mL of water added, so 5 mg in 2 mL is 2.5 mg/mL.
- U-100 insulin syringe
- A syringe marked for U-100 insulin, which has 100 units in each mL. The 0.3 mL, 0.5 mL and 1 mL sizes hold 30, 50 and 100 units, and other scales such as U-40 exist, which is why the U-100 marking matters.
- Unit (on a syringe)
- One mark on a U-100 insulin syringe, equal to 0.01 mL whatever the barrel size. A unit is a volume, not an amount of peptide, and it is not the same thing as an IU.
- mcg per unit
- What one unit on a U-100 syringe holds after mixing: vial mg × 10 ÷ water mL. A 5 mg vial with 2 mL of water holds 25 mcg per unit, the number the site's charts and calculator are built on.
Mixing and storage
Most peptides arrive as a dry powder and are mixed with a liquid before research use. These are the words on the vials, the water and the charts. The mixing charts show the water Matthew uses for each vial.
- Reconstitution
- Mixing a dry peptide powder with a liquid, called the solvent or diluent, to make a solution. The amount of liquid sets the concentration but does not change how much peptide is in the vial.
- Lyophilized
- Freeze-dried. The product is frozen and its water removed under vacuum, leaving a dry powder or cake that is more stable than a liquid, which is why peptides are supplied this way.
- Bacteriostatic water
- Sterile water with 0.9% benzyl alcohol added as a preservative, so a vial can be entered more than once. It is the liquid in Matthew's videos, books and charts, and its labeling says it is not for use in newborns.
- Benzyl alcohol
- The preservative in bacteriostatic water and bacteriostatic saline, usually at 0.9%. It slows the growth of bacteria rather than sterilizing, and products containing it are labeled not for newborns because of reported toxicity in that group.
- Sterile water
- Purified, sterile water with nothing added: no preservative, salt or buffer. Without a preservative it usually comes in single-use containers, labeled to be used once and the rest discarded.
- Saline
- Sodium chloride 0.9%, water with about the same salt level as body fluids. It comes plain or as bacteriostatic saline with benzyl alcohol, and Matthew's books describe it as used less often than bacteriostatic water for peptides.
- Beyond-use date
- The date after which an opened or mixed product should not be used. It comes from the label, and in US clinical practice an opened multi-draw vial is generally dated and discarded 28 days after first entry unless the maker gives a different date.
- Blend
- One vial holding two or more peptides, labeled with the total and the split, for example 10 mg (5/5). Every amount drawn from it carries each peptide in that same ratio.
- Stack
- Two or more compounds combined in the same research, each from its own vial. Unlike a blend, each one is mixed and measured separately, with its own math.
Testing and labels
A certificate of analysis is where most of these terms show up, along with a few that appear on vial labels. The guide to reading a COA covers each part of a report in order, and the free reader kit has a one-page COA checklist.
- COA (certificate of analysis)
- A lab report with the test results for one batch of a product, usually identity and purity and sometimes amount, endotoxin and sterility. It applies only to the lot it names.
- Lot number
- The code that identifies one production batch, also called a batch number. The lot on a COA should match the lot printed on the vial.
- HPLC
- High-performance liquid chromatography, the standard test for peptide purity. The sample is pushed through a packed column that separates its parts, and a detector records each one as a peak.
- Chromatogram
- The graph an HPLC test produces, showing detector signal over time. The large peak should be the peptide and smaller peaks are impurities, so a purity figure without its chromatogram can't be checked.
- Mass spectrometry
- A test that measures the mass of molecules, often called mass spec or MS. On a COA it confirms identity: the measured molecular weight should match the peptide's known weight.
- Purity
- The share of the tested material that is the intended peptide, usually given as an HPLC percentage. It shows how clean the sample is, not how much peptide is in the vial or whether it is sterile.
- Net peptide content
- The share of the powder's weight that is actually peptide. It is usually lower than the HPLC purity, because the powder also holds water and salts that HPLC does not count.
- Endotoxin
- Fragments of the outer wall of certain bacteria that can trigger fever and inflammation even when no live bacteria remain. Labs measure it with the LAL test and report it in endotoxin units (EU).
- Sterility test
- A test for living bacteria and fungi, done by placing samples in growth media and watching for growth over about two weeks. A product can pass sterility and still carry endotoxin, so the two are separate tests.
- Third-party lab
- A testing lab independent of the seller and the maker. Accreditation to ISO/IEC 17025 means an outside body has assessed the lab's competence for the tests listed in its scope.
- Research use only (RUO)
- A label stating that a product is sold for laboratory research, not for use in people or animals. It describes the intended use and is not a purity grade, a test result or an approval.
How peptides work
These terms come up in every library profile: what a peptide is made of, what it binds to, how long it lasts and how it enters the body. Each profile in the Peptide Library puts them in context for one compound.
- Amino acid
- The building blocks of peptides and proteins. The body uses 20 standard amino acids, and the order they are linked in, called the sequence, decides what a peptide does.
- Peptide
- A short chain of amino acids joined by peptide bonds. There is no strict cutoff, but chains of more than about 50 amino acids are usually called proteins, which is why IGF-1 LR3 is described as a small protein.
- Analog
- A molecule built to resemble a natural one, usually changed to last longer or bind differently. Sermorelin and tesamorelin are GHRH analogs, and cagrilintide is an amylin analog.
- Receptor
- A protein on or in a cell that a particular molecule binds to, like a key in a lock. Binding switches on a signal inside the cell.
- Agonist
- A molecule that binds a receptor and activates it, while an antagonist binds and blocks it. Semaglutide is a GLP-1 receptor agonist, and retatrutide, which activates three receptors, is called a triple agonist.
- Half-life
- The time it takes for the amount of a substance in the blood to fall by half. Natural GHRH is cleared within minutes, while CJC-1295 with DAC, whose DAC linker binds it to the blood protein albumin, has a half-life of about a week.
- Pharmacokinetics
- How the body absorbs, spreads, breaks down and clears a substance over time. Half-life and bioavailability are both pharmacokinetic measures.
- Bioavailability
- The share of a substance that reaches the bloodstream in active form. It is 100% by definition when given into a vein, while most peptides taken by mouth are broken down in digestion, so their oral bioavailability is very low.
- Subcutaneous
- A route meaning under the skin, into the layer of fat above the muscle. Insulin and many approved peptide medicines are labeled for this route.
- Intranasal
- A route meaning through the nose, as a spray or drops. Semax and Selank were developed in Russia as nasal drops, and the route is studied for compounds aimed at the brain.
- Oral
- A route meaning by mouth. Stomach acid and digestive enzymes break most peptides down, which is why oral semaglutide (Rybelsus) is made with an absorption enhancer.
- GHRH
- Growth hormone-releasing hormone, the brain signal that tells the pituitary to release growth hormone, with somatostatin as the opposing brake. Sermorelin, tesamorelin and CJC-1295 act on the GHRH receptor.
- GHRP (ghrelin mimetic)
- Growth hormone-releasing peptides, such as GHRP-2, GHRP-6, hexarelin and ipamorelin. They mimic ghrelin, the stomach's hunger hormone, at its receptor, which is why some of them raise appetite.
- Secretagogue
- Anything that prompts the body to release a substance. Growth hormone secretagogues, including GHRH analogs, GHRPs and the non-peptide MK-677, prompt the pituitary to release its own growth hormone.
- IGF-1
- Insulin-like growth factor 1, a 70-amino-acid hormone made mainly by the liver when growth hormone signals it. It carries out much of growth hormone's work and is commonly measured as a marker of growth hormone activity.
- GLP-1
- Glucagon-like peptide-1, a gut hormone released after eating that helps the pancreas release insulin when blood sugar is high and slows stomach emptying. Semaglutide, the active ingredient of Ozempic and Wegovy, is a lab-made, longer-lasting version.
- GIP
- Glucose-dependent insulinotropic polypeptide, the other main incretin, a gut hormone released after eating. Tirzepatide, the active ingredient of Mounjaro and Zepbound, acts on the GIP and GLP-1 receptors.
- Glucagon
- A pancreas hormone best known for raising blood sugar between meals. Retatrutide is designed to act on the glucagon receptor as well as the GLP-1 and GIP receptors.
- Amylin
- A hormone the pancreas releases with insulin after meals, involved in fullness and in slowing stomach emptying. Cagrilintide is a long-acting amylin analog.
- Melanocortin
- A family of hormones and their five receptors, MC1R to MC5R, involved in skin pigment, appetite, inflammation and sexual function. Melanotan II and PT-141 act on melanocortin receptors.
- Peptide bioregulator
- A term from Vladimir Khavinson's research group in Russia for very short peptides they propose can change gene activity in specific tissues. Epithalon and Bronchogen belong to this group, and the idea has had little testing outside it.
- Cycle
- In Matthew's books and in online discussion, a planned period on a compound followed by a break. Breaks are often discussed in terms of desensitization, when a receptor responds less after steady stimulation.
Study types
Library profiles say plainly what kind of evidence stands behind each claim. These terms run roughly from early lab work in cells to large human trials, and knowing which kind of study a finding comes from matters more than any single headline about it.
- In vitro
- Latin for in glass: experiments on cells or tissues in a dish or test tube. They show what can happen at the cell level, not what happens in a living body.
- In vivo
- Latin for within the living: research in a whole living animal or person, as opposed to cells in a dish.
- Animal study
- Research in mice, rats or other animals, usually the step before human trials. Many compounds in the library have mostly animal data, and results in animals often do not carry over to people.
- Case report
- A published description of one patient, or of a few in a case series. It can flag a possible effect or side effect, but with no comparison group it can't show cause.
- Randomized controlled trial (RCT)
- A study in which people are assigned by chance to the treatment or a comparison, such as a placebo. Random assignment makes the groups alike, so differences in results are more likely due to the treatment.
- Placebo
- An inactive look-alike given to the comparison group in a trial. In a double-blind trial, neither the participants nor the researchers know who got which until the end.
- Phase 1, 2 and 3 trials
- The stages of testing a drug in people. Phase 1 is small and checks safety and how the body handles the drug, phase 2 looks for early effects in people with the condition, and phase 3 tests it in large groups against placebo or standard care.
- Meta-analysis
- A study that pools the results of several earlier trials on the same question, usually as part of a systematic review that searches for every relevant study by a set method. It is only as good as the trials it combines.
- Investigational
- Still being tested in clinical trials and not approved as a medicine. Library profiles say when a compound is at this stage.
