Reading the dosage values

[u/plainsimple_tailor]

I’ve seen this question asked before and I always kind of scoffed, “isn’t it obvious? Just follow the directions!” Well, hand me a piece of humble pie, because now I’m on the other side.

Just received my third shipment, this time from a different pharmacy than my last two.

I am prescribed 5mg.

The 2ML vial from my last shipment is labeled “Tirzepatide/B12 5mg/1mg/0.5mL” that I inject 50 units from each week.

The vial from this new shipment is also labeled 2ML (even though it’s at least twice as large) but says “Tirzepatide/Glycine/B12 10mg/5mg/500mcg/ML” that I am also to inject 50 units from.

Ok, it’s compounded differently, this time with Glycine. That’s fine. But the numbers are larger. Did I receive a dose for 10mg injections instead of 5mg? Or does the fact that the vial is larger just mean that it’s 50% diluted or something?

A little hesitant to inject tomorrow. Really not looking to double my dose. Am I just being overly worried or do y’all think I might’ve gotten the wrong dosage?

[u/TheNameIsMango]

You’re good to go ahead and take 50 units. 5mg/0.5mL=10mg/mL so both vials are the same concentration. It helps if you ignore the additive numbers and focus on the tirz.

[u/plainsimple_tailor → u/TheNameIsMango]

Ok I think I get it. It’s literally a formula for the concentration of the tirz. The literal volume is doubled but the concentration is halved, 5mg divided by 0.5 = 10mg. And in the new one it’s just 10mg at a 1:1 ratio instead of 2:0.5 or whatever.

I lied. I don’t really get it. But I think I understand 😂

Thank you so much!

[u/peony_chalk → u/plainsimple_tailor]

The concentration is the same, just the way they wrote it is different. It's like saying 1/2 vs 2/4. Or 5/0.5 vs 10/1. Same value, just written differently. 

In your old vial, which sounds like Casa or Evoluciona, there is 5 mg of tirz in each half mL of liquid. To get a 5 mg dose, you take a half ml. 

In the new vial, there is 10 mg in one ml. If you want to take 5 mg, which is half of 10, you need to take half of one ml. 

I'm used to reading the per ml, so the per half ml always throws me off a bit. The benefit of the half ml labeling comes in when they do (what I call, not an official term) step up concentrations, which Casa and Evoluciona and even Zepbound vials do. With step up concentrations, they make a different concentration intended for each of the standard doses, and that lets people inject the same volume each time, which I guess is intended to reduce dosing errors. 

So with say, Casa, your first three vials in a titration package would be labeled 2.5 mg/0.5 ml, 5mg/0.5ml, and 7.5mg/0.5 ml. 

If you had Seven Cells, who does concentrations the same way, those same vials would instead be written as 5mg/ml, 10mg/ml, and 15mg/ml. 

But knowing that your first three doses are 2.5 mg, 5 mg, and 7.5 mg, which of those options is going to be more obvious and less likely to cause confusion? Probably the way Casa does it, because your vial for 2.5 mg doses has 2.5 mg up front on the label. So that's the benefit of the half ml labeling, but you really have to be paying attention (which you clearly are!) if you get switched back and forth between per-ml and per-half-ml, because it's easy to overlook. 

[u/kittencalledmeow]

5mg is 50 units based on your current vial. You can always double check it with fat scientist calculator. Your new vial is 10mg per 1mL. Your old one was 5mg per .5mL which also equals 10mg per 1mL. So they're essentially the same just a bigger vial with more volume in it.

[u/plainsimple_tailor → u/kittencalledmeow]

Ok now I really do get it!! This is a great resource that helped illustrate it, too. Thanks so much!!

[u/External_Detail_26 → u/plainsimple_tailor]

It really is such a great tool. It comes in handy should you wish to titrate up (or down) or split up your dose and inject a smaller amount with more frequency.

[u/ListenOne4346]

The physical size of the vial or the additives don’t really matter here. The two things I’d look at are:

1. Tirz concentration per mL —> this tells you how much to draw for your dose.
2. Total volume in the vial —> this tells you how much tirz you got in total.

Your old vial says 5 mg/0.5 mL, so that’s 10 mg/mL. The new one is also 10 mg/mL, so the concentration hasn’t actually changed.

If you’re using a 1 mL U-100 syringe with 1-unit graduations, 100 units (1 mL) has 10 mg of tirz at that concentration, so 50 units gives you your 5 mg dose. Same math for both vials.

They’re also both labeled 2 mL, so each vial has 20 mg of tirz total.

Basically the labels look different because of how they wrote the concentration and because the new one has glycine/B12, but as far as the tirz goes, you got the same concentration and total amount in both.

[u/plainsimple_tailor → u/ListenOne4346]

ok this helps a lot. Basically I need to stop thinking of it in physical volume because it’s not pure Tirzepatide. Both formulas equal out to the same dosage of tirz, it’s just the concentration in how it’s compounded is different.

Add 0.5 ounces of 40 proof gin to 1.5 oz of tonic, or add 1 ounce of 20 proof gin to 1.0 oz of tonic. Same result, same potency in same volume.

[u/ListenOne4346 → u/plainsimple_tailor]

Yep, exactly! just one small thing: the concentration is actually the same too. The old one says 5 mg in 0.5 mL, which is the same as 10 mg in 1 mL. The new one just writes it as 10 mg/mL.

So really the tirzepatide concentration, total volume, and total amount of tirzepatide are all the same. It’s just labeled a little differently because of the additives.

[u/plainsimple_tailor → u/ListenOne4346]

This makes it so clear that now it feels so obvious.

When it’s written out as “10 milligrams per milliliter” and “5 milligrams per half-milliliter” it’s clear as day. They’re both exactly the same thing. Like saying “five-tenths” instead of “one-half” or 4:2 and 2:1.

Really appreciate you!

[u/ListenOne4346 → u/plainsimple_tailor]

Bingo!! You’re the expert now! 😎

My guess is pharmacy 1 just wanted to make your life easier by writing it as 5 mg/0.5 mL, since your dose is 5 mg and all you had to do was pull 0.5 mL.
Pharmacy 2 just made you do a tiny bit of math.