Peptide dosing protocols look intimidating when you first encounter them. You see abbreviations like mcg, IU, and BW. You see terms like titration, loading phase, and maintenance dose. You see reconstitution ratios that involve decimal points and unit conversions.

None of it is as complicated as it looks. Once you understand the building blocks, any protocol becomes readable. Here’s how to break it down.

Start With the Units

Everything in peptide dosing comes down to units of measurement. Getting these wrong causes errors that cascade through every calculation after.

The three units you’ll see most often:

• mg (milligram) — one thousandth of a gram. Many peptides are supplied in vials labeled in mg. Semaglutide comes in 5 mg vials. BPC-157 often comes in 5 mg vials.
• mcg (microgram) — one thousandth of a milligram, or one millionth of a gram. Many peptide doses are expressed in mcg. BPC-157 is typically dosed at 250 to 500 mcg per day. That’s 0.25 to 0.5 mg from a 5 mg vial.
• IU (International Unit) — used for some peptides like HGH. IU is a biological activity measure, not a weight measure. It cannot be directly converted to mg without knowing the specific peptide’s potency.

The most common source of confusion is mixing up mg and mcg. If a protocol says 500 mcg and you read it as 500 mg, you’d be calculating a dose 1,000 times higher than intended. Always double-check which unit a dose is expressed in before doing any math.

Understanding Reconstitution

Most research peptides arrive lyophilized — freeze-dried into a white powder. Before you can measure a dose, you have to reconstitute the peptide by adding bacteriostatic water (BAC water) to the vial.

The ratio of peptide to water determines the concentration of your solution. That concentration is what lets you calculate how many units in a syringe equal a specific dose.

Example: you have a 5 mg vial of BPC-157. You add 3 mL of BAC water. Your concentration is now 5 mg divided by 3 mL, which equals 1.67 mg per mL, or 1,670 mcg per mL.

If your target dose is 500 mcg, you divide 500 by 1,670 to get 0.3 mL. On a U-100 insulin syringe — the most commonly used syringe type for research peptides — 0.3 mL equals 30 units on the barrel.

The reconstitution ratio you choose matters. A higher volume of BAC water makes each unit on the syringe represent a smaller dose — easier to measure small amounts accurately. A lower volume of BAC water gives a more concentrated solution — useful if you need a large dose in a small injection volume.

What a Titration Schedule Actually Means

Many peptide protocols, especially for GLP-1 agonists like semaglutide and tirzepatide, use a titration schedule. This means the dose starts low and increases gradually over weeks or months.

Semaglutide’s standard titration looks like this: 0.25 mg weekly for four weeks, then 0.5 mg, then 1.0 mg, then 1.7 mg, then 2.4 mg maintenance. Each step lasts four weeks.

The reason for titrating is tolerability. GLP-1 agonists cause nausea, especially early on. Starting low and increasing slowly lets the body adjust. Jumping straight to a maintenance dose causes significantly more side effects.

Not all peptides require titration. BPC-157, for example, is typically started at a standard dose from day one. Growth hormone secretagogues are often titrated to manage tolerability. The protocol will tell you which approach applies.

Loading Phase vs. Maintenance Phase

Some protocols — particularly for healing peptides like TB-500 — split into two distinct phases.

The loading phase uses a higher dose over a shorter period to saturate tissues and establish a therapeutic level faster. TB-500 loading is typically 2 to 5 mg twice weekly for four to six weeks.

The maintenance phase follows with a lower dose to sustain the effect. TB-500 maintenance is usually 2 mg once weekly for another four to eight weeks.

The logic is similar to loading creatine — you front-load to reach effective levels faster, then use a smaller dose to maintain them. Not every peptide uses this structure, but when a protocol includes it, the phases should be followed in order.

How to Evaluate a Dosing Reference

Not all dosing information online is equally reliable. When researching peptide dosages for any specific compound, look for references to the underlying studies. A protocol that cites Phase 2 or Phase 3 clinical trial data, or peer-reviewed preclinical research, is more trustworthy than one that cites another blog post or community consensus.

Specifically look for:

• The source of the dosing range — was it a clinical trial, an animal study, or anecdotal community data? These carry very different weight.
• The administration route — subcutaneous injection, intramuscular, oral, and intranasal peptides have different bioavailability. A dose optimized for subcutaneous use may be completely different from an oral dose of the same compound.
• The cycle length — many peptide protocols specify on and off periods. Using a peptide indefinitely without cycling is not standard in most research protocols and may affect receptor sensitivity over time.
• The purity and form of the compound — protocol doses are typically calculated assuming a specific purity level. Impure or degraded peptides will not deliver the expected dose even if you measure correctly.

The Syringe Question

Most people researching peptide dosing will use U-100 insulin syringes for subcutaneous administration. The barrel is marked in units from 0 to 100, where 100 units equals 1 mL.

This means 10 units equals 0.1 mL, 50 units equals 0.5 mL, and so on. Once you know your solution’s concentration in mg per mL or mcg per mL, the math to convert a target dose into syringe units is straightforward division.

Where people go wrong: mixing up the syringe unit markings with IU measurements. A U-100 syringe unit is a volume measurement. An IU is a biological activity measurement. They are not the same thing and cannot be substituted for each other.

One Final Point on Accuracy

In research contexts, dose accuracy matters more than it might seem. Peptides are active in small amounts. Variation of even 10 to 20% from an intended dose can produce meaningfully different outcomes in research data.

This is why reconstitution math, correct syringe selection, and reliable dosing references are not minor details. They’re the foundation that everything else is built on.

Take the time to get the math right before anything else.