Page last checked 2026-08-20

Reconstitution · Semaglutide

Semaglutide reconstitution calculator

Pick the vial, the water you added and the dose. Get the exact draw in units for the syringe in your hand.

Step 1 of 4

How many mg are in your vial?
Vial strengthamount printed on the vial
How many mL of water did you add?
Bacteriostatic water addedhow much water you added
What dose do you want to convert?
Target doseenter the dose you want to convert
mg
This vial holds 5 mg in total.
Which syringe are you using?
Syringe typematch the label on your syringe
U-100 insulin syringe · 1 mL · lines every 2 units · 1 unit = 0.01 mL

Draw to

10.0units

0.10 mL · 2.50 mg/mL · 25 mcg per unit · 20 doses per vial

Easy to read on this syringe. Draw to the 10-unit line. No rounding is needed.

5 mg ÷ 2 mL = 2.50 mg/mL
→ 25 mcg/unit · 0.25 mg = 0.100 mL = 10.0 units

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Show the math and syringe details

Can this syringe show the result clearly?

Easy to read on this syringe. 10.0 u is exactly the 10-unit line on a U-100 — no rounding error at all.

Want an easier syringe number?

This setup is already easy to read. Changing the water between 0.5 and 3 mL would not put 0.25 mg closer to a line on this U-100 syringe.

Adding more water makes the mixture less concentrated, so the same dose uses more syringe units. It does not change how much peptide is in the vial.

This setup is in the address bar — every input is part of the link.

Educational math, not medical advice — dosing decisions belong to a licensed clinician. The tabs above also plan a schedule week by week and count how many doses one vial holds.

How to use the calculator

STEP 1
Enter the amount in the vial
Use the total amount printed on the vial, in mg.
STEP 2
Enter the water you added
Use the amount of water added to that vial, in mL.
STEP 3
Enter the dose you want to convert
Choose mg or mcg, then match the result to your syringe.

Semaglutide is the drug in Wegovy, Ozempic and Rybelsus. It copies a gut hormone called GLP-1, which helps control appetite and blood sugar. People take Wegovy for long-term weight management, and Ozempic or Rybelsus for type 2 diabetes.

All three products have FDA approval. Wegovy and Ozempic are weekly injections; Rybelsus is a daily tablet, and each has its own schedule.

Examples using a 5 mg Semaglutide vial

Each row starts with the same 5 mg vial and changes only the amount of water. More water makes the mixture less concentrated, so the same dose uses more syringe units.

◆ How the water amount changes the resultdose used: 0.25 mg

For a 5 milligram vial: bacteriostatic water added, resulting concentration, micrograms per U-100 unit, and the draw for a 0.25 mg dose.
Water added	Concentration	Per U-100 unit	Draw for 0.25 mg	Nearest syringe line
1 mL	5.00 mg/mL	50.0 mcg	5.0 u · 0.050 mL	6 u · 20.0% off
2 mL	2.50 mg/mL	25.0 mcg	10.0 u · 0.100 mL	exactly 10 u

The vial, water and dose shown here are the calculator’s starting example for Semaglutide. Replace them with your own values. Every result in the table is calculated from those inputs.

Drawn from once a week at 0.25 mg, a 5 mg vial yields 20 doses — about 20.0 weeks of supply. That runs past the 28 days the mixed vial keeps for, which arrives with 16 doses — 4 mg — still in the vial.

A small starting dose in a strong solution

Semaglutide starts lower, in milligrams, than anything else here with a label behind it. That makes the first weeks the hardest to draw accurately, and the vial you mix decides how hard.

3Open the mixing details — 3 notes

A pen measures for you; a vial does not

The approved products dial a dose and stop. Nothing about that transfers to a vial. Here the strength comes from what you added, and the dose comes from a mark you have to find yourself. A pen removes both steps.

It also means no figure printed on a pen box describes this vial. The milligrams match. The way you get them out does not.

Why the first dose sits badly on the barrel

Take the largest vial on this page and add the least water. You have made the strongest solution it allows. The starting dose then covers a couple of units, where one mark either way moves it by a fifth.

The page’s other water volume doubles that reading for the same dose. On a compound whose whole first month sits at the bottom of the scale, that is the most useful choice on the page.

The mistake: mixing small because the powder looks small

A few milligrams of semaglutide is a smear at the bottom of the glass. It looks like it needs hardly any water, so people add the smaller volume and feel generous doing it. The powder is not what made the draw unreadable. That choice was.

There is also a clock worth noticing. The labeled schedule holds each step for four weeks. This page’s sourced window for a mixed vial runs in weeks too. So one step of the schedule and one mixed vial tend to run out together.

One molecule, sold as a pen, a tablet and a powder

The dose figures here are taken from an approved label. That label covers three products, and one of them is swallowed. A milligram of the tablet and a milligram in this vial are not the same amount arriving, and nothing on this page bridges them.

4Read the supporting evidence — 4 supporting notes

A milligram you swallow is not a milligram you inject

One semaglutide brand is a tablet. It contains the same molecule but is taken by mouth and uses different amounts.

Three names, and a quoted figure rarely says which one it came from

Semaglutide is sold under three brand names. Two are injections approved for different conditions and use different dose schedules. The third is a tablet.

Three vial sizes, and one course crosses all of them

Three powder-vial sizes are documented, and the largest is several times the smallest. No approved semaglutide product is sold as a powder vial.

The ladder here has two endings

Most of this page’s rungs are steps on the way up, each held for a set number of weeks. The top two are different. The label treats both as places to stay.

Units to dose at 2.50 mg/mL

Mix 5 mg into 2 mL and one U-100 unit carries 25.0 mcg. The table shows how much peptide is in each numbered syringe line. These are conversion examples, not suggested doses.

10Open the unit conversion table — 10 rows

Numbered U-100 syringe lines converted to volume and mass at 2.50 milligrams per milliliter.
U-100 line	Volume	Mass (mcg)	Mass (mg)
10 u	0.10 mL	250 mcg	0.25 mg
20 u	0.20 mL	500 mcg	0.5 mg
30 u	0.30 mL	750 mcg	0.75 mg
40 u	0.40 mL	1,000 mcg	1 mg
50 u	0.50 mL	1,250 mcg	1.25 mg
60 u	0.60 mL	1,500 mcg	1.5 mg
70 u	0.70 mL	1,750 mcg	1.75 mg
80 u	0.80 mL	2,000 mcg	2 mg
90 u	0.90 mL	2,250 mcg	2.25 mg
100 u	1.00 mL	2,500 mcg	2.5 mg

Where repeated Semaglutide doses settle

Each weekly dose lands before the last one has cleared. So the level in the body climbs for a while, then holds steady. The half-life here is 7 days, which leaves 50% of a dose still there a week later. The level settles at about 2.00× what one dose gives. It gets 95% of the way there after 5 doses, roughly 4 weeks in.

9Open the weekly build-up table — 9 rows

For each dose: the estimated level just after it and just before the next dose, compared with the first dose, plus how close the peak is to the long-term level.
Dose	Level after	Level before the next	Share of long-term level
1	1.00×	0.50×	50%
2	1.50×	0.75×	75%
3	1.75×	0.87×	87%
4	1.88×	0.94×	94%
5	1.94×	0.97×	97%
6	1.97×	0.98×	98%
7	1.98×	0.99×	99%
8	1.99×	1.00×	100%
Plateau	2.00×	1.00×	100%

Half-life Wegovy (semaglutide) — FDA-approved Prescribing Information (DailyMed) · retrieved 2026-08-20. Every other figure is arithmetic on that half-life and the interval.

These are ratios, not blood levels. Turning them into an actual concentration would need more information than the cited source provides. The simple model is also only an approximation of how a drug really behaves in a body. The Accumulation tab plots the same math at whatever interval you pick.

How the math works

Concentration — divide the amount in the vial by the water you added: mg ÷ mL = mg/mL. This tells you how many mg are in each mL.
Volume — the dose divided by that concentration: dose ÷ (mg/mL) = mL.
Units — on a U-100 syringe one unit is 0.01 mL, so mL × 100 = units. A U-40 unit is 0.025 mL, so the wrong barrel is a 2.5× error. That is why the calculator asks which one you have.
Rounding gap — the exact draw against the nearest syringe line: |exact − nearest line| ÷ exact × 100 = % difference.

Medically reviewed by Jennifer Montecillo, MD · non-practicing medical reviewerReviewed 2026-08-20open the primary sources

Useful guides for this calculation

The math is only one part of the question. These guides cover the compound, published doses, side effects, mixing steps and supplies.

How long each semaglutide step is held before the next

2 published semaglutide dose values, each linked to the original source.

The FDA dates that ended compounded semaglutide

Compounding semaglutide under 503A ended 2025-04-24, under 503B 2025-05-22.

The molecule behind Wegovy, Ozempic and Rybelsus

Published half-life: 7 days.

From semaglutide milligrams to syringe lines

Change the water and every semaglutide row moves together, which is what the table is for.

The label instructions behind injecting semaglutide

A guide exists for semaglutide only because an approved label’s instructions do.

Tirzepatide vs semaglutide, from the semaglutide side

SURMOUNT-5 studied 751 adults for 72 weeks. This sits beyond semaglutide.

Questions readers ask

How do you calculate reconstitution?

Divide the vial’s milligrams by the milliliters of water, then read one U-100 unit as a hundredth of a milliliter of the result. A 5 mg vial in 2 mL is 2.5 mg/mL, so each unit carries 25 micrograms.

Semaglutide is where that last step earns its keep. The labeled starting quantity is 0.25 mg, which comes to 10 units at 25 micrograms per unit. Mix 10 mg into 1 mL instead and the same dose is 2.5 units, where one mark ruins the draw.

How do I reconstitute 20 mg of semaglutide?

The preset vials are 2, 5 and 10 mg. For a 20 mg vial, the same formula gives 10 mg/mL with 2 mL of water or 5 mg/mL with 4 mL.

At 10 mg/mL the 0.25 mg starting quantity draws 2.5 units, the weakest reading anywhere in this page’s range. A 20 mg vial also holds 80 of those starting doses. Both facts point one way: a bigger vial wants more water.

How much BAC water for 10 mg of semaglutide?

Either 1 mL or 2 mL, and the choice doubles or halves how far up the barrel the first dose sits. 1 mL is 10 mg/mL and puts 0.25 mg at 2.5 units; 2 mL is 5 mg/mL and puts it at 5.

Neither is a large number, which is this compound’s particular problem. Its whole first month sits at the bottom of the barrel, and the labeled schedule holds each step for four weeks. This page’s sourced window for a mixed vial is 28 days, so one step and one mixed vial tend to end together.

How to reconstitute a 10mg bottle of semaglutide?

You measure the water with a syringe too, and on a U-100 barrel 1 mL is one full draw while 2 mL is two. Most mixing guides skip that step entirely.

After that the vial holds 10 mg in whatever went in, and the pen you may have used before measures nothing for you here. The labeled doses run from 0.25 mg up to 2.4 mg. A 10 mg vial covers 40 starting doses, or 4 at the full maintenance quantity.

1primary source, each with the day we read it — open the documents used on this page

Wegovy (semaglutide) — FDA-approved Prescribing Information (DailyMed)retrieved 2026-08-20FDA label