Is there standard way I should calibrate a new pen?

[mrmors]

I looked up 'calibrate' and 'calibration' but didn't find much useful.

For many months I've stuck with regular insulin syringes, but I figured I'd test a gensupen2 for one of my daily doses.

I loaded a blank cartridge with tap water, used a needle tip to prime out the air, then removed the tip. After that I ran these tests:

-With a 1ml, 31gauge syringe attached/injected into the cartridge, I attempted to backwards inject 10units x2

-With a 3ml, 27gauge syringe attached/injected into the cartridge, I attempted to backwards inject 10units x2

-With the 31gauge micro tip needle back on, I injected 10 units into an empty 1ml syringe that had its plunger pulled out, x2

-With the 31gauge micro tip needle back on, I injected 10 units into an empty 3ml syringe that had its plunger pulled out, x2

I honestly can't think of another way to test it.

BUT, across those 4 different tests I got 4 different results, and none delivered 0.1ml of water on the receiving end. Every test landed 10-20% off, yet consistently 10-20 out. For example, the test into the 3ml syringe gave me roughly 90% accuracy, both times, spot on. The 1ml syringe was the same, giving me 80% spot on.

So I really don't know what I should set the gauge to for a standard dose. I've been guessing and putting it at 24, trying to get a 20unit dose, since that seems roughly in the right range based on my testing.

It looks like the dial accuracy and the actual delivery accuracy line up better IF you use a larger gauge needle like 27 or lower; with super fine needles the pen seems to struggle to deliver accurately.

How do those of you who use pens regularly handle this? Is there an easy trick for calibration that I'm overlooking?

 

[bbbilly]

I remember watching a few videos by the peptide critic over on youtube. In them, he first primes the pen, then attaches a regular easy touch syringe to the tip and pushes roughly 10 units, checking whether the syringe actually reaches the 10 unit mark. After that, he keeps using that syringe until he's ready to rely on the pen alone.

edit to make this clearer.

What he does is insert the syringe into the cartridge's rubber stopper exactly like you would when drawing from it. Then he dials the test units and injects them through the needle into the body while leaving the plunger in place. The plunger simply gets forced back as the pen plunger is pressed. If the result is off, honestly I don't know what you could do beyond just figuring out what the delta is. Say it comes up 5 units short on every single unit test, then you know it's consistently 5 under and you just have to keep that in mind. But if it isn't at least consistent in how far off it is, or if the gap grows or shrinks depending on how many units you push, then I wouldn't even bother using it. As far as I know, these pens can't be adjusted, so if they're off, you're stuck with it.

 

[eidos]

All 4 of your approaches work, though how easy and exact they are shifts with syringe size — still, they really shouldn’t give you results that differ so much. When you repeat one method several times, do the numbers stay steady?

I no longer bother with v2 pens (the kind that have a flat top you can push down). I keep some v1, v3, ergo2, and the Gansulin, which is the one I like best; all of them are accurate and reliable. Most importantly, they push the piston with the correct force and don’t miss a click.

A cartridge issue can crop up now and then: the sliding seal that serves as the piston may be installed upside down. Look at an insulin syringe and you’ll notice the thick end sits on the plunger rod, while the thin end faces the liquid. The pen’s cartridge ought to match that orientation.

 

[Pocket]

When you draw backwards with the syringes, do you grab new ones each time? Or do you rinse them out with water beforehand? Because air trapped in the needle can compress, which would skew what you read. If you rinse the syringe first so some water stays in the needle, you ought to get a closer measurement of what the pen delivers. I don't know whether that's what's going on for you, but I'd like to help eliminate it as a possibility.

 

[mrmors]

@bbbilly for my part, it's inaccurate, though the error stays the same, and right now I've settled on a delta of 4 for a 20 unit dose, so I take 24 instead. That gets me closest to 20 units in a 1ml syringe on average, comparing reverse injection with injecting into a syringe that has no plunger.

@eidos repeating the different methods several times does give me consistent results. Still, I've stuck with what I get using the 31 gauge tips, since that's how I'd actually deliver it.

@Pocket at first I used a fresh syringe for every test, but I didn't really note the first result down because I figured it might throw things off—the plunger doesn't reach the very end of the chamber—so I decided to run a few tests after the water had already been in there once, and each time the numbers came out about the same. a lower gauge means more accurate delivery, but the needles I'd be using are high gauge.

 

[Pocket]

mrmors said:

@bbbilly for my part, it's inaccurate, though the error stays the same, and right now I've settled on a delta of 4 for a 20 unit dose, so I take 24 instead. That gets me closest to 20 units in a 1ml syringe on average, comparing reverse injection with injecting into a syringe that has no plunger.

@eidos repeating the different methods several times does give me consistent results. Still, I've stuck with what I get using the 31 gauge tips, since that's how I'd actually deliver it.

@Pocket at first I used a fresh syringe for every test, but I didn't really note the first result down because I figured it might throw things off—the plunger doesn't reach the very end of the chamber—so I decided to run a few tests after the water had already been in there once, and each time the numbers came out about the same. a lower gauge means more accurate delivery, but the needles I'd be using are high gauge.

Ahh, I see. It's good that you eliminated that possibility. Still, it's unfortunate that your pen isn't measuring accurately.

 

[eidos]

mrmors said:

@bbbilly for my part, it's inaccurate, though the error stays the same, and right now I've settled on a delta of 4 for a 20 unit dose, so I take 24 instead. That gets me closest to 20 units in a 1ml syringe on average, comparing reverse injection with injecting into a syringe that has no plunger.

@eidos repeating the different methods several times does give me consistent results. Still, I've stuck with what I get using the 31 gauge tips, since that's how I'd actually deliver it.

@Pocket at first I used a fresh syringe for every test, but I didn't really note the first result down because I figured it might throw things off—the plunger doesn't reach the very end of the chamber—so I decided to run a few tests after the water had already been in there once, and each time the numbers came out about the same. a lower gauge means more accurate delivery, but the needles I'd be using are high gauge.

What matters most is doing the same thing every time. That way, you can spot whether an error is systematic, and then tweak either your concentration or how many clicks you use accordingly.