How many units is a 300 mcg Semax dose?

With a 10 mg Semax vial reconstituted in 2 mL of bacteriostatic water (5 mg/mL, or 5000 mcg/mL), a 300 mcg dose works out to 300 divided by 50 mcg per unit, which is 6 units on a U-100 insulin syringe.

How much bacteriostatic water goes into a Semax vial?

It depends on the concentration you want. A common reference point is 2 mL for a 5 mg or 10 mg vial, which keeps typical research amounts in a readable unit range. Use the calculator to test other volumes and find one that lands the target amount on a round syringe mark.

Is Semax FDA-approved?

No. Semax is not FDA-approved for any use in the United States. It has a use history in Russia as a registered nasal-drop product, but that regulatory status does not transfer to the lyophilized research vials this calculator's math applies to.

Does a Semax reconstitution calculator handle both mg and mcg?

Yes. Vial labels are almost always in milligrams while research amounts are often 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.

Semax Reconstitution Calculator: Water & Syringe Math

By PeptCalc Research — Medically reviewed by David Mansour, MD — Last reviewed August 16, 2026

Semax vials are labeled in milligrams, and turning that label into an exact syringe draw is the arithmetic a Semax reconstitution calculator is built to handle. This is a reference for that math: 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 Semax reconstitution 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 solution's volume in mL multiplied by 100 on a U-100 syringe. That formula doesn't change because the vial holds Semax instead of another peptide — only the vial's own mass and water volume matter.

Semax at a glance

Semax is a synthetic peptide built from a fragment of adrenocorticotropic hormone (ACTH), a hormone the body produces as part of the stress-response system, with additional amino acids attached to extend its stability. It was developed by a Russian research program and has a use history there as a registered nasal-drop pharmaceutical product, studied primarily in connection with cognitive and neurological research contexts. That Russian registration is a meaningfully different regulatory pathway than FDA approval, and it does not extend to the lyophilized, vial-based research form sold in the U.S. research-compound market.

Semax 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 is. For a peptide that shares Semax's Russian research origin, see Selank vs Semax.

Typical research concentration

Semax 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)
30 mg	2 mL	15 mg/mL (15,000 mcg/mL)

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

The math

Step 1: Calculate concentration

Concentration = vial mass ÷ water volume

10 mg vial + 2 mL water = 10 ÷ 2 = 5 mg/mL (5000 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

5000 mcg/mL ÷ 100 = 50 mcg per unit

Step 3: Convert the target amount to units

Units = target amount (mcg) ÷ mcg per unit

Worked example. A 10 mg Semax vial reconstituted in 2 mL of bacteriostatic water is 5 mg/mL, or 5000 mcg/mL, which is 50 mcg per unit. A 300 mcg research reference amount from that vial is 300 ÷ 50 = 6 units. A 600 mcg amount from the same vial is 600 ÷ 50 = 12 units.

Compare that to the same 10 mg vial reconstituted in just 1 mL of water instead: 10 ÷ 1 = 10 mg/mL, or 10,000 mcg/mL, which is 100 mcg per unit. That same 300 mcg amount is now 300 ÷ 100 = 3 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 10 mg vial and a 300 mcg target:

Water added	Concentration	mcg per unit	Units for 300 mcg
1 mL	10,000 mcg/mL	100 mcg/unit	3 units
2 mL	5,000 mcg/mL	50 mcg/unit	6 units
5 mL	2,000 mcg/mL	20 mcg/unit	15 units

None of these rows is more correct than another — 300 mcg is 300 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 peptide reconstitution calculator finds the water volume that lands a specific amount on a round unit mark.

Reconstitution process

Gather the Semax 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 Semax 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. Semax vial labels are in milligrams; research amounts are often described in micrograms. 1 mg equals 1000 mcg, and misreading one for the other produces a 1000x error.
Treating Russian nasal-drop registration as equivalent to FDA approval. It isn't. Semax has not gone through FDA review, and that registration history doesn't apply to the lyophilized research vials this calculator's math applies to.
Reusing a unit count across a different water volume. As the table above shows, 300 mcg is 6 units at one concentration and 3 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 Semax reconstitution 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 how Semax compares to a related Russian-origin research peptide, see Selank vs Semax.