How many units is a 250 mcg Selank dose?

With a 5 mg Selank vial reconstituted in 2 mL of bacteriostatic water (2500 mcg/mL), a 250 mcg dose works out to 250 divided by 25 mcg per unit, which is 10 units on a U-100 insulin syringe.

How much bacteriostatic water goes into a 5 mg Selank vial?

It depends on the concentration wanted. A common reference point is 2 mL, which gives 2500 mcg/mL and keeps typical research amounts in a readable unit range. Use the calculator to test other volumes and find one that lands a target amount on a round syringe mark.

Is Selank FDA-approved?

No. Selank has no FDA approval for any use in the United States. It has a use history in Russia as a registered nasal-drop product, but that status does not extend to the lyophilized research vials this calculator's math applies to, and none of the figures here describe an approved or recommended human dose.

Does a Selank dosage calculator handle both mg and mcg?

Yes. Vial labels are almost always in milligrams while research amounts are typically described in micrograms. 1 mg equals 1000 mcg, and the calculator converts between the two automatically once a vial size, water volume, and target amount are entered.

Selank Dosage Calculator: Reconstitution & Syringe Units

By PeptCalc Research — Medically reviewed by David Mansour, MD — Last reviewed August 15, 2026

Selank vials are labeled in milligrams, while research amounts are typically described in micrograms — the exact conversion a Selank dosage calculator is built to handle. This is a reference for the arithmetic behind that vial: how vial size and bacteriostatic water volume set concentration, and how concentration turns a target amount into an exact draw on a U-100 insulin syringe. It is written for research purposes only and is not medical advice.

What the calculator does

A Selank dosage calculator only needs three numbers to do its job: vial size, water volume, and target amount. The peptide calculator handles the conversion in two directions:

Forward mode — enter vial size, water volume, and target amount, and it returns the syringe units to draw.
Reverse mode — enter vial size, target amount, and a desired unit count, and it returns the water volume that produces it.

Both modes run on the same formula: concentration equals mass divided by water volume, and units equal that volume in mL multiplied by 100 on a U-100 syringe. That formula doesn't change because the vial holds Selank instead of another peptide — only the vial's own mass and water volume matter.

Selank at a glance

Selank is a synthetic peptide derived from tuftsin, a naturally occurring peptide involved in immune signaling, with additional amino acids attached to extend its stability. It was developed by a Russian research program and has a use history there in registered nasal-drop form, most often discussed in connection with anxiety-related behavior research rather than the cognitive framing more often associated with the related peptide Semax, which comes out of the same research lineage but is derived from a different parent molecule.

Selank is not FDA-approved for any use in the United States. It is sold as a lyophilized research compound, not as a drug or supplement, and nothing here describes a use recommendation. It describes reconstitution arithmetic, which is identical regardless of a compound's regulatory status or how established its research base is. For a closer look at how Selank relates to Semax specifically, see Selank vs Semax.

Typical research concentration

Selank most commonly reaches researchers as lyophilized powder in vials in the 5 mg to 10 mg range. Reconstituted in 2 mL of bacteriostatic water, a reference point chosen because it keeps typical research amounts on readable syringe marks:

Vial size	Water added	Concentration
5 mg	2 mL	2.5 mg/mL (2500 mcg/mL)
10 mg	2 mL	5 mg/mL (5000 mcg/mL)

These are reference points, not requirements — the peptide dosage calculator recalculates concentration for any vial size and water volume actually on hand.

The math

Step 1: Calculate concentration

Concentration = vial mass ÷ water volume

5 mg vial + 2 mL water = 5 ÷ 2 = 2.5 mg/mL (2500 mcg/mL)

Step 2: Convert concentration to mcg per unit

A U-100 insulin syringe divides 1 mL into 100 units, so:

mcg per unit = concentration (mcg/mL) ÷ 100

2500 mcg/mL ÷ 100 = 25 mcg per unit

Step 3: Convert the target amount to units

Units = target amount (mcg) ÷ mcg per unit

Worked example. A 5 mg Selank vial reconstituted in 2 mL of bacteriostatic water is 2500 mcg/mL, which is 25 mcg per unit. A 250 mcg research reference amount from that vial is 250 ÷ 25 = 10 units. A 100 mcg amount from the same vial is 100 ÷ 25 = 4 units.

Compare that to a 10 mg vial in the same 2 mL of water: 10 ÷ 2 = 5 mg/mL, or 5000 mcg/mL, which is 50 mcg per unit. That same 250 mcg amount is now 250 ÷ 50 = 5 units — a smaller draw from a higher-concentration vial, even though the amount in mcg hasn't changed at all.

Choosing a water volume

Water volume is the lever that sets how large a given amount reads on the syringe. For a 5 mg vial and a 250 mcg amount:

Water added	Concentration	mcg per unit	Units for 250 mcg
1 mL	5000 mcg/mL	50 mcg/unit	5 units
2 mL	2500 mcg/mL	25 mcg/unit	10 units
5 mL	1000 mcg/mL	10 mcg/unit	25 units

None of these rows is more correct than another — 250 mcg is 250 mcg regardless of which row it comes from. A larger draw is generally easier to measure precisely on a U-100 barrel than a very small one, since a one-unit misread is a bigger proportional error at the low end. Reverse mode on the free peptide calculator finds the water volume that lands a specific amount on a round unit mark.

Reconstitution process

Gather the Selank vial, bacteriostatic water, a U-100 insulin syringe, and alcohol swabs.
Swab both vial stoppers with alcohol.
Draw the water volume the chosen concentration calls for.
Inject it slowly down the inside wall of the vial, not directly onto the powder.
Swirl gently until fully dissolved — don't shake.
Confirm the resulting concentration matches what was entered into the calculator before drawing an amount.

For the general mixing walkthrough that applies to any peptide vial, see how to reconstitute peptides.

Storage

Reconstituted Selank is generally kept refrigerated and protected from light. Unreconstituted lyophilized powder is far more stable than the mixed solution, which is why vials ship dry. Track the date each vial was reconstituted, particularly if more than one vial is in use at different concentrations.

Common mistakes

Confusing mg and mcg. Selank vial labels are in milligrams; research amounts are typically described in micrograms. 1 mg equals 1000 mcg, and misreading one for the other produces a 1000x error.
Assuming Selank and Semax share a dosing profile because they share a research lineage. They're derived from different parent molecules and studied in different contexts. The reconstitution math is identical; the compounds are not.
Reusing a unit count across a different water volume. As the table above shows, 250 mcg is 10 units at one concentration and 5 units at another. A unit count only means something relative to the specific concentration it was calculated from.
Using a syringe that isn't U-100. Every unit conversion here assumes 100 units equal 1 mL. A different syringe scale changes the math entirely.
Skipping a fresh concentration check after reconstitution. Confirm the math before drawing, especially when switching between vial sizes.

Used as a Selank dosage calculator, the peptide calculator skips the arithmetic and returns exact syringe units, with reverse mode available for finding a water volume that lands an amount on a clean mark. For more on how Selank compares to a closely related peptide, see Selank vs Semax.