Beginner's Guide to Peptides

A comprehensive starting point for understanding what peptides are, how they work, and how to read and use research protocols. No prior knowledge assumed.

What Are Peptides?

Peptides are short chains of amino acids — the same building blocks that make up proteins. The distinction is length: peptides are generally defined as chains of 2 to 50 amino acids, while longer chains are classified as proteins. Your body produces thousands of peptides naturally, and they serve as signaling molecules, hormones, and biological regulators.

Some examples you may already know without realizing they're peptides: insulin (51 amino acids, regulates blood sugar), oxytocin (9 amino acids, involved in social bonding), and growth hormone (191 amino acids — technically a protein but closely studied in the peptide research community).

In research contexts, "peptides" usually refers to synthetic versions of naturally occurring peptides, or novel analogs designed to mimic them — produced in a laboratory and provided as lyophilized (freeze-dried) powders for research purposes.

How Do Peptides Work?

Peptides work by binding to specific receptors on or inside cells, triggering a biological response. Think of it as a key fitting into a lock: the peptide is the key, the receptor is the lock, and the biological effect is what happens when the door opens.

Different peptides target different receptors, which is why they have such varied effects. A growth hormone releasing peptide (like GHRP-6) binds to ghrelin receptors in the pituitary, triggering GH release. A GLP-1 agonist (like semaglutide) binds to GLP-1 receptors in the pancreas and brain, affecting insulin secretion and appetite. BPC-157 interacts with multiple pathways related to tissue repair and inflammation.

The key concept is specificity: each peptide has a specific target, a specific dose range where it's active, and a specific half-life that determines how long it remains active in the body. This is why dosage protocols matter — the same peptide at the wrong dose, wrong frequency, or wrong route of administration may produce no effect, an unintended effect, or unwanted side effects.

Major Peptide Categories

How Peptides Are Supplied

Research peptides arrive as a lyophilized powder — a white or off-white cake at the bottom of a small sealed glass vial. The label indicates the peptide name and total amount (e.g., "BPC-157 5mg"). This powder must be reconstituted — dissolved in a liquid diluent — before it can be used. The lyophilized form exists because peptides are far more stable as dry powder than in solution, giving much longer shelf life before reconstitution.

Reconstitution: Turning Powder into Solution

Reconstitution is the single most important practical skill in peptide research handling.

What You Need

• The peptide vial (lyophilized powder)
• Bacteriostatic water (BAC water) — sterile water with 0.9% benzyl alcohol as preservative
• Insulin syringe — typically a U-100, 1 mL syringe
• Alcohol swabs — to sterilize the vial stopper before each puncture

The Process

1. Clean the rubber stopper of both the peptide vial and the BAC water vial with an alcohol swab.
2. Draw the desired amount of BAC water into the syringe. The amount determines the concentration — more water = more dilute.
3. Inject slowly into the peptide vial, aiming the stream against the glass wall — not directly onto the powder.
4. Swirl gently — never shake. Let the powder dissolve completely (typically 1–2 minutes, sometimes up to 10).
5. Refrigerate the reconstituted vial immediately at 2–8°C (35–46°F).

Understanding Units & Measurements

Unit confusion is the #1 source of dosing errors for beginners. Three measurement systems are in use, and they measure different things:

Weight: mg and mcg

mg (milligrams) and mcg (micrograms) measure how much peptide you're working with by weight. The relationship is: 1 mg = 1,000 mcg. Some peptides are dosed in milligrams (e.g., semaglutide at 0.25 mg) and others in micrograms (e.g., Ipamorelin at 200 mcg). Confusing the two creates a 1,000-fold error.

Volume: mL and Syringe "Units"

mL (milliliters) measure how much liquid you're drawing. On a standard U-100 insulin syringe, markings go from 0 to 100 "units," where 100 units = 1 mL. So each "unit" on the syringe = 0.01 mL of liquid. These are volume marks, not dose marks — they tell you nothing about peptide content until you know the concentration.

Potency: IU (International Units)

IU measure biological potency for specific peptides — primarily HGH (≈3 IU per 1 mg) and HCG. IU are not the same as syringe "units." When a protocol says "inject 2 IU of HGH," it's specifying potency. You still need to calculate the volume based on your reconstitution concentration.

Syringes: Types and How to Read Them

Almost all peptide protocols use insulin syringes because they're designed for small, precise volumes and have thin needles (typically 28–31 gauge) suitable for subcutaneous injection. The three most common types:

• U-100 (1 mL) — 100 units = 1 mL. Most common. Each unit = 0.01 mL. Best for doses requiring 5–100 units of liquid volume.
• U-100 (0.5 mL, "half-unit" syringe) — Same scale but only holds 50 units. Markings are more spread out — better for small-volume doses.
• U-50 / U-20 syringes — Less common; 50 or 20 units = 1 mL. Useful for very high-concentration solutions.

For doses under 10 units on a standard U-100, use a 30- or 50-unit capacity syringe instead for much better measurement precision.

Routes of Administration

• Subcutaneous (Sub-Q): Most common for research peptides. Injection into the fatty tissue just below the skin, typically abdomen, outer thigh, or upper arm. 45–90° needle angle.
• Intramuscular (IM): Used for some peptides. Deeper injection into muscle tissue. Faster absorption than sub-Q for some compounds.
• Intravenous (IV): Required for some compounds (e.g., Cerebrolysin). Requires clinical or laboratory setting.
• Intranasal: Some peptides (Adamax, Selank, Semax) are researched via nasal insufflation.
• Oral: A few compounds (5-Amino-1MQ, some AICAR research) can be studied orally; most peptides are degraded by gastrointestinal proteases and require parenteral administration.