Forum › Dosing & Titration

Actual number of doses per vial

10 replies8 peopleJun 14, 2026☆ Follow
Summary

why fewer doses come out of a reconstituted peptide vial than the math predicts

Users report getting 3-4 doses instead of the expected 5 from a 10-12 mg vial after filtering and multiple draws. The shortfall is attributed to liquid retained in filters, luer-lock dead space, and repeated syringe manipulations. Suggestions include using more diluent to reduce relative loss, air-purging syringes, or switching to fixed-needle or pen systems. Everyone agrees the gap is normal with standard technique rather than a calculation error.

What this discussion establishes

Nothing here is advice.

10 replies · 8 people
PlainTimber80archiveopening postJun 14

Been using Reta with my research subject for several months. Noticed the actual number of doses pulled from each vial falls short of the calculated amount. For example, 10 mg mixed with 1 mL bac water at a 2 mg dose should produce five 20-unit shots, yet only three or four come out. Ran the numbers through multiple reconstitution calculators without finding an error. Using a 4 mm filter. Last batch was 12 mg reconstituted with 1 mL bac water plus a 0.5 mL purge, making 12 mg in 1.5 mL total for a 2 mg dose at 25 units. After three injections the vial looks nearly empty with only one dose left. Any idea what is going wrong or is this typical?

LikeSame experienceReply
WarmHarbour28archiveJun 14

Why switch between milliliters and units when describing the dilution?

LikeSame experienceReply
ClearBeacon24archiveJun 14
↳ replying to @PlainTimber80 (opening post)

No need for RS on here.

LikeSame experienceReply
SlowSparrow49archiveJun 14

What kind of syringe are you using both for reconstitution and for injections? Luer-lock types can have up to 0.1 mL or 10 units of dead space. That could mean losing a full dose per draw. Try taking the needle off, pulling in air, and pushing it through to clear some of the space.

LikeSame experienceReply
QuietThistle70archiveJun 14

Any time liquid moves through a syringe and needle a small amount stays behind. Splitting a vial into many doses multiplies those small losses compared with one or two larger draws. Even so, with careful technique the total should only be a unit or two per vial.

LikeSame experienceReply
SlowSparrow49archiveJun 14
↳ replying to @QuietThistle70

That is true for fixed-needle syringes, but luer-lock setups have more dead space. When you add bac water, then pull the solution out, filter it into another vial, and swap needles several times without clearing the space, you can lose close to 20 units. An air purge reduces it but does not eliminate it. For my TRT shots I leave a 5-10 unit air bubble in the luer-lock syringe so the bubble pushes most of the liquid out.

LikeSame experienceReply
ClearBeacon24archiveJun 14
↳ replying to @SlowSparrow49

I handle those after straining and put in a small bit more solution to balance or wash.

LikeSame experienceReply
SteadySignal69archiveJun 14

The filter keeps some liquid and so does the syringe; it is hard to get every last drop from the vial. Every additional draw wastes a bit more. The filter in particular holds quite a bit. With 1 mg total and 0.2 mg doses you really only have four usable doses once you count the losses from one or more syringe actions plus the filter. Using more bac water spreads the same fixed loss over a larger volume so the percentage lost drops. Pens with cartridges cut the waste because you only draw from the vial once and pay a single small loss inside the cartridge instead of losing several units on every injection.

LikeSame experienceReply
ClearBeacon24archiveJun 14
↳ replying to @SteadySignal69

I toss in some more bac to offset or clear it.

LikeSame experienceReply
GreyAlder39archiveJun 14

It is not a math issue but a technique one. Every handling step introduces small measurement errors because syringes are not precision micropipettes, and some liquid is always left behind. To reduce the quantity lost, dilute more so the same volume loss represents less active material. Check what actually remains in the vial at the end. Pens make this easier because they usually have a scale.

LikeSame experienceReply
PatientFenwick55archiveJun 16

The missing dose is lost during the filter step, either inside the filter itself or in the luer-lock needle hub, both of which have more dead space than an insulin syringe. You can test the difference with an empty vial, a waste container, and plain water: draw 20 units five times with an insulin syringe, then repeat with a luer-lock setup. Even without a filter the luer-lock dead space removes a noticeable amount.

LikeSame experienceReply

Related discussions

Add your experience

If you have tried it, this topic is still open. Sign in to reply — it takes a minute.

Sign inCreate an account
Actual number of doses per vial · ZyraTrack Community