How Much BAC Water for 10 mg Retatrutide? (and Other Common Vials)

Key takeaways

We do not publish a water volume or a units figure for retatrutide. It is an investigational drug with no approved product, no pharmacy that may compound it and no label, so any number would be arithmetic on a vial whose contents nobody has verified.
The water never sets the dose. It sets the concentration, which decides how many syringe units carry a dose; the risk sits in the milligrams in the vial, the dose chosen and the units drawn, and with a research vial all three are guesses.
Harm has already been reported: a woman admitted after four dose-escalated weekly injections of a product reported to contain retatrutide, and a man with type 1 diabetes with ketosis and kidney injury after an online product. With compounded semaglutide vials, FDA has documented patients injecting 5 to 20 times the intended dose.
The trials used once-weekly doses of 1 to 12 mg, started at 2 mg or 4 mg and escalated by protocol under clinical monitoring. Those are studied doses, not a protocol.
For vials a pharmacy can legally dispense, the worked examples are below: compounded sermorelin, Egrifta WR and SV, and GLP-1 solutions that need no water at all.

The direct answer: we do not give one. Retatrutide has no approved product anywhere, no US pharmacy may compound it, and the only lawful access is a clinical trial or Lilly's physician-requested early access program, so every 10 mg vial for sale is a research-labeled product with no pharmacy label to check a calculation against; the retatrutide profile has the full status. Our rule, set out with the BAC water calculator, is that we publish how much water and how many units only for products a US pharmacy can legally dispense. This page covers what the water actually does, the dosing harms already reported with gray-market retatrutide, the doses the trials used, and worked examples for the vials people can legally be prescribed. Our BPC-157 page answers the same question for another peptide no pharmacy may compound.

Why we will not put a number on a 10 mg vial

Three reasons, all practical.

The 10 mg is a claim. No regulator, pharmacist or clinician has checked what is in a research vial. The author of the 2026 type 1 diabetes case notes that the composition, purity and dosing accuracy of online research peptides may be uncertain (Branine 2026). The best measured example is semaglutide: researchers who bought lyophilized semaglutide vials from illegal online pharmacies received three, which held 29 to 39 percent more semaglutide than labeled at a purity of 7 to 14 percent against an advertised 99, and one contained endotoxin (Ashraf 2024). Correct arithmetic on a wrong label is a wrong dose.
There is nothing to check the arithmetic against. For a prescribed vial, a calculation checks the pharmacy's label. For a research vial it is the only instruction, written by whoever sold it. The Egrifta WR example below shows that even a manufacturer's vial can differ from simple division.
A mixing chart is what FDA treats as drug marketing. FDA's March 31, 2026 warning letter to Gram Peptides covered retatrutide, tirzepatide and bacteriostatic water sold with research-use labels, and its five August 24, 2026 letters named retatrutide among other products. In each, dosing guidance, reconstitution calculators and bundled bacteriostatic water were the evidence that the vials were drugs for people (FDA, Gram Peptides) (ArentFox Schiff 2026).

What the water does, and what it does not

Bacteriostatic water dissolves a freeze-dried powder and sets its concentration: milligrams in the vial times 1,000, divided by the milliliters added, gives micrograms per milliliter. It does not change how much drug is in the vial or in a dose. It changes how many syringe units carry that dose. In a 6 mg vial of compounded sermorelin, 3 mL makes a 300 mcg dose read as 15 units, and 1.5 mL makes the same 300 mcg read as 7.5 units. Half the water, half the units, same dose.

Two consequences follow. The water volume is never the dangerous number on its own; the dangerous numbers are the milligrams actually in the vial, the dose chosen and the units drawn. And a units figure copied from someone else's chart is right only if their vial, their water and their dose all match yours. A pharmacy label fixes all three; a research vial fixes none. The forward arithmetic is in the peptide calculator, and how many units are in 1 mL explains the syringe scale.

The dosing harms already reported

The published harms from gray-market retatrutide are few, recent and specific.

Unsupervised escalation. A woman in her mid-20s was admitted with five days of nausea, vomiting and loose stools that did not respond to three antiemetics. The cause was four once-weekly, dose-escalated injections of an unverified product reported to contain retatrutide, given in a wellness setting by a self-described life coach with no medical qualification. She had not thought of the injections as medication (Buzzi 2026).
A glucagon agonist meeting insulin-dependent diabetes. A man in his mid-30s with type 1 diabetes developed severe vomiting, diarrhea, high blood sugar, ketones peaking at 4.3 mmol/L and acute kidney injury after self-injecting an online product marketed as retatrutide, followed by recurrent low blood sugar during recovery. A Shigella infection was also found, so causation is uncertain; the trials never enrolled people with type 1 diabetes (Branine 2026).
Starting too high. In the phase 2 trial, gastrointestinal side effects were dose-related and were partly reduced by starting at 2 mg rather than 4 mg (Jastreboff 2023). A chart that skips the starting step skips the one dosing lesson the trials published.
Units versus milligrams. Retatrutide is dosed weekly in milligrams, and a research vial is dosed by drawing units. That is the format behind the compounded semaglutide errors FDA described in 2024: patients injecting 5 to 20 times the intended dose, patients told to draw 5 units who injected 50, and prescribers who converted milligrams to units wrongly (FDA 2024). A poison-center series reported two 10-fold self-dosing errors with compounded semaglutide vials (Lambson 2023). Those were pharmacy products with a labeled concentration; a research vial has neither.

The retatrutide profile covers the side effects seen in the trials, including skin dysesthesia and a dose-related rise in heart rate.

What the trials actually used

Trial	Doses studied (once weekly, under the skin)	Starting dose and escalation	Population	Mean weight change
Phase 2, 2023	1, 4, 8 and 12 mg	The 4 mg and 8 mg arms started at 2 mg or 4 mg, the 12 mg arm at 2 mg; the 2 mg start reduced gastrointestinal events	338 adults with obesity, or overweight plus a weight-related condition, without diabetes; 48 weeks	8.7, 17.1, 22.8 and 24.2 percent versus 2.1 percent on placebo (Jastreboff 2023)
TRIUMPH-1, 2026	4, 9 and 12 mg	Stepwise escalation; the schedule is not given in the published abstract	2,339 adults with obesity, without diabetes; 80 weeks	17.6, 23.7 and 25.0 percent versus 3.9 percent, by intention to treat (Jastreboff 2026)

Two things in that table never reach a sales page: the trials started low and escalated by protocol, and every participant was screened, monitored and seen by investigators. The milligram figures travel; the rest stays behind.

Other common vials: worked examples for prescribed products

For vials a US pharmacy can legally dispense, here is the arithmetic. The label on your own vial overrides every figure in this section.

Vial	Diluent and volume	Concentration	Example dose	Units on a U-100 syringe
Compounded sermorelin 6 mg	3 mL bacteriostatic water (provider instructions)	2,000 mcg/mL	300 mcg (an example prescription)	15
Compounded sermorelin 9 mg	4.5 mL bacteriostatic water	2,000 mcg/mL	300 mcg	15
Compounded sermorelin 15 mg	7.5 mL bacteriostatic water	2,000 mcg/mL	300 mcg	15
Egrifta WR (tesamorelin) 11.6 mg	1.3 mL bacteriostatic water, supplied	8 mg/mL, as the label states	1.28 mg (label dose)	16
Egrifta SV (tesamorelin) 2 mg	0.5 mL sterile water for injection, supplied	4 mg/mL	1.4 mg (label dose)	35, injected at once
Zepbound multi-dose vial	Nothing: it is a solution	4.17 to 25 mg/mL by strength	2.5 to 15 mg (label doses)	0.6 mL for every strength

Compounded sermorelin

How much bacteriostatic water · sermorelin, 6 mg vial

Peptide in vial (mg)Prescribed dose (mcg)Units you want per dose (U-100)

Bacteriostatic water to add: 3 mL
Resulting concentration: 2,000 mcg/mL; 2 mg/mL
Doses per vial: 20

The water you add changes the concentration, never the dose. If your pharmacy label states a reconstitution volume, use the label, not this calculator. Units are on the U-100 scale (100 units = 1 mL). This tool does not recommend a dose.

One telehealth provider's patient instructions pair a 6 mg vial with 3 mL, a 9 mg vial with 4.5 mL and a 15 mg vial with 7.5 mL of bacteriostatic water, which puts all three at 2,000 mcg/mL (Defy). For a prescription written as 300 mcg, the example our sermorelin profile uses, that is 15 units from any of the three, with 20, 30 or 50 doses per vial; the beyond-use date on the label still caps how long a vial is used. Pharmacies that add 3 mL to every size produce 2,000, 3,000 and 5,000 mcg/mL instead, so the same 300 mcg is 15, 10 or 6 units, the convention in our sermorelin dosage chart. The published trials gave 1 to 2 mg per injection, 50 to 100 units at 2,000 mcg/mL; 300 mcg is a common prescription, not a studied dose.

Tesamorelin: Egrifta WR and Egrifta SV

How much bacteriostatic water · Egrifta WR label check

Peptide in vial (mg)Prescribed dose (mcg)Units you want per dose (U-100)

Bacteriostatic water to add: 1.45 mL
Resulting concentration: 8,000 mcg/mL; 8 mg/mL
Doses per vial: 9.1

Egrifta WR comes with its own bacteriostatic water: 1.3 mL into the 11.6 mg vial, a stated concentration of 8 mg/mL, and a daily dose of 1.28 mg in 0.16 mL, or 16 units; one mixed vial lasts 7 days at room temperature (Egrifta WR label). Look at what the calculator asks for: 1.45 mL, not 1.3. Simple division most likely misses the volume the dissolved powder adds, and the label reflects the manufacturer's measurement, so the label wins. Egrifta SV, the 2 mg single-dose vial, is mixed with 0.5 mL of the supplied sterile water instead, for a 1.4 mg dose of 0.35 mL (35 units) injected immediately, with the rest discarded (Egrifta SV label). Same molecule, two diluents: one vial serves a week and needs a preservative, the other serves one dose. The tesamorelin profile covers the drug.

Tirzepatide and semaglutide: nothing to add

This is also the answer to the tirzepatide reconstitution chart people search for: a legal tirzepatide product has no such chart. Every Zepbound vial is a solution, single-dose vials of 2.5 to 15 mg in 0.5 mL and multi-dose vials holding four 0.6 mL doses, already preserved with benzyl alcohol (Zepbound label). Compounded semaglutide and tirzepatide are normally dispensed as solutions too, in multiple-dose vials with the concentration on the label, and adding water dilutes them. A tirzepatide powder sold for mixing is a research product; FDA's Gram Peptides letter covered tirzepatide alongside retatrutide (FDA, Gram Peptides). Our compounded semaglutide versus tirzepatide guide covers the legal options.

If you want retatrutide

The legitimate routes are a clinical trial or Lilly's physician-requested early access program for adults with refractory obesity and serious complications. Lilly plans to submit retatrutide to FDA in the first quarter of 2027 (Lilly 2026), which puts any approval in late 2027 at the earliest. Until then tirzepatide and semaglutide are approved, labeled and available, at $299 to $449 a month for Zepbound and $349 for Wegovy through the manufacturers' cash programs, per our cost guide. The legal tracker records any change.

Bottom line

How much bacteriostatic water goes into 10 mg of retatrutide is the wrong question, because the water never decides the dose and nothing about a research vial is verified: not the milligrams, not the sterility, not the chart. The doses that produced the trial results came with screening, slow escalation and a clinician. For the vials a pharmacy can legally dispense, the arithmetic is simple and the label settles it; for retatrutide in October 2026, there is no label to settle anything.

Frequently asked questions

+How much BAC water for 10 mg retatrutide?

We do not publish a volume or a units figure for retatrutide. It is an investigational drug: no product is approved anywhere, no US pharmacy may compound it, and the 10 mg vials sold online are research-labeled products whose content nobody has verified. The water only sets the concentration and never fixes the dose; the risks lie in the unverified milligrams, the dose chosen and the units drawn, and a mixing chart cannot fix any of them.

+Is retatrutide legal?

Possessing it is not a crime; selling it for human use is. Retatrutide is not approved anywhere, cannot be compounded by any US pharmacy, and cannot be prescribed outside a clinical trial or Lilly's physician-requested early access program. FDA's warning letters of March 31 and August 24, 2026 rejected research-use labels on retatrutide sold with dosing instructions, calculators and bacteriostatic water.

+What is grey market retatrutide?

Vials sold online as 'reta' with a research-use disclaimer, usually as a powder to mix with bacteriostatic water and dose from a seller's chart. Nobody has tested what is in them. In 2026 two published case reports described hospital admissions after products reported to contain retatrutide: refractory vomiting after four dose-escalated injections given by a wellness coach, and ketosis with kidney injury in a man with type 1 diabetes.

+Does tirzepatide need to be reconstituted?

Not if it is a legal product. Zepbound comes as a solution in pens, single-dose vials and multi-dose vials, and compounded tirzepatide is normally dispensed as a solution in a multiple-dose vial at a concentration printed on the label. Adding water dilutes it. A tirzepatide powder sold for mixing is a research product of the kind FDA warned sellers about in 2026.

+How many units is 1 mL for peptides?

100 units on a U-100 insulin syringe, so 10 units is 0.1 mL. Units measure volume, so how much drug a unit holds depends entirely on the concentration of the vial. A units figure copied from someone else's chart is only valid for an identical vial, water volume and dose.

+When will retatrutide be available?

Not before late 2027 at the earliest. Lilly said in July 2026 that it plans to submit retatrutide to FDA in the first quarter of 2027, and a standard review takes about ten months. Until approval, the lawful routes are a clinical trial or Lilly's physician-requested early access program.

+What are the risks of retatrutide peptide?

In the trials: dose-related nausea, vomiting, diarrhea and constipation, a dose-related rise in heart rate, and skin dysesthesia at the higher doses. Research vials add their own risks: unknown content and purity, no sterility assurance, unsupervised dose escalation, units-versus-milligram errors and use in people the trials excluded, such as those with type 1 diabetes.