the insulin syringe thing finally clicked for me and I want to write it down
the insulin syringe thing finally clicked for me and I want to write it down, which sounds obvious until you try to state the evidence for it.
Research-use-only material is not approved for human use, so treat everything in this thread as arithmetic about solutions rather than instructions for a person.
I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.
Spent 16 weeks confused about this until somebody drew the table for me. 5mg, 1mL, 5mg/mL, 2mg is 40 units. That is the whole thing.
Corrections welcome, especially the pedantic ones. Pedantry is how this board earns its reputation.
best — the order this archive was captured in
The lyophilised cake displaces a small volume, so the true concentration is very slightly lower than the arithmetic suggests. It is a fraction of a percent and it is dwarfed by fill tolerance.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
Wrote the date on the vial as well as the concentration after losing track of which one was opened first.
Careful — that arithmetic is wrong. 10mg in 2mL is 5mg/mL, so 2mg draws to 40 units, not what you wrote.
if the maths gives you a fraction of a unit, change the concentration
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
bacteriostatic water has the preservative, sterile water does not
Reconstituted at 2mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 5mg/mL on the glass before I put the cap back.
Reconstituted at 2mL when I meant to use a different volume.
Right, and the arithmetic behind it: 20mg in 2mL is 10mg/mL, so 2mg is 20 units.
That is sterile water, not bacteriostatic.
dilara_szabo has the units point exactly right. They are a volume on the barrel and nothing else.
if the maths gives you a fraction of a unit, change the concentration
This is the sentence that makes the rest unnecessary. Write it on the vial and the problem is gone.
do the arithmetic before you reconstitute, not while holding a syringe
write the concentration on the vial in marker, that is the whole post
The dead space question sent me down a rabbit hole for a week. It is a fraction of a unit and it is the same every draw.
If your calculation produces a fraction of a unit, the concentration is wrong for your dose. Change the water volume until the numbers land on whole units.
a U-100 syringe reads 100 units to the millilitre, every time
units are a volume on a U-100 syringe, not a dose
more water is not more drug, it is the same drug in a bigger volume
more water is not more drug, it is the same drug in a bigger volume
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
reconstituting at a round concentration makes every later dose easy
reconstituting at a round concentration makes every later dose easy
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
Shook the first vial because nobody told me not to. It was fine, but I have swirled every one since.
aim the stream at the glass wall, not at the cake
the number you write down is the number you will trust at 6am
The arithmetic in full: concentration is mass over volume, so 20mg into 1mL gives 20mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1mg is 1 divided by 20 millilitres, which is 5 units.
15mg into 3mL is 5mg/mL, and 2.5mg of that is 50 units
Show the arithmetic — where did the unit figure come from?
- 1write the concentration on the vial in marker, that is the whole post9 comments in this branch · started by u/ines_lindqvist
- 2if the maths gives you a fraction of a unit, change the concentration7 comments in this branch · started by u/RetaAndRegret2