My observations on sub-q test and insulin syringes

Billegitimate

New member
I see frequent comments about back-loading, or comments about how you can't draw with an insulin syringe, or how it takes forever.

Today I actually took the time to measure my test draw and injection.

I use a BD .3cc insulin syringe with a 31gauge, 5/16" needle. The barrel size of .3cc is optimal because the small barrel generates very large pressures. The 5/16" needle is much better than a 1/2" needle because it minimizes the length of the very narrow passage that the oil has to go through. And the 31g is awesome because I usually inject without feeling a thing!

I will eventually make a video of this so there's no arguing the ability to use the tiniest imaginable needle, but here's the process:

1) I put my vial in front of my wife's hairdryer, which is set to medium, just before I brush my teeth. By the time I'm done brushing my teeth the vial and oil inside is nice and warm.

2) Swipe the top of the vial with alcohol. A nice advantage is it evaporates almost instantly on the warm stopper.

3) With the syringe still capped, draw back the plunger to the point of intended draw.

4) Uncap syringe, insert into vial, and inject the air into the vial.

5) Draw back about .02cc on the syringe until oil begins to flow into the syringe, then push the plunger back up to pinch off the bubble and let it float up to the top. This takes 3-4 seconds. The rest of the draw, the oil will flow around that bubble and leave it up there at the top.

6) Draw the plunger back until the bubble is .02-.03cc and maintain that bubble size as the oil flows. So I'm basically pulling the bubble down to .03, and about the time it gets back to .02 I'm pulling again. I continue this process until I'm just a little past my intended draw.

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(This exact method is important! If you just yank the plunger down, air will work around the plunger and into the barrel rather than oil from the vial. Then the oil stops flowing and you will now be someone who says you can't get the oil to draw into an insulin syringe. You can, it works fine, but if you pull back so quickly that the vacuum is too great and the plunger lets air sneak past it then you just have a syringe full of air.)
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7) Tap the syringe and inject the remaining bubble of air back into the vial so you now have the intended amount in the syringe.

8) Inject

9) Lift heavy things, have a positive outlook on life, want your wife 24/7.

As I said, I'll make a video because some of this is more easily shown. I'll include my sub-q shots on the video as well. I have developed a technique I like for those as well.

Now, as to all the stuff about unable to draw, have to backload, takes forever: I timed it today. It took 28 seconds to draw .15ml. It took 13 seconds to inject it. If I round up to 30 and 15, then that's 45 seconds draw and injection time per .15ml, or 30 seconds per .1ml. Typical .5ml weekly dose means 150 seconds time drawing and injecting. I don't know how fast the giant harpoons are when one goes IM, but if it's half that time then that's a 75 seconds/week savings.

And in exchange, I have no scaring, no bruising, no pain, no bleeding. Heck, if the IM shots could occur in 1 second, I'll still take 2 1/2 minutes a week to go the painless easy route. Oh, and I don't waste .05-.1ml per shot with the dead space at the top of a big syringe. The insulin needs are zero dead space.

Two final notes:

1) Not heating the vial increases the draw time 40-60% but doesn't really seem to affect the injection time.

2) I also sometimes use tuberculin syringes that are .5cc and 27g 3/8" needles. They're a little faster than this even with a cold vial. If you're taking closer to 1cc a week, then these may be better for you. I take less than .5cc a week.

If anyone is curious, I'll get back on with exact part numbers for ordering either syringe. I've tried a bunch and the two I use are by far the best for sub-q.
 
Nice writeup. One comment: the bubbles that form when you draw back on the plunger "too much" are not air that gets past the plunger (it forms a very tight seal), but cavitation bubbles: little areas of vacuum created by the low pressure
 
Nice writeup. One comment: the bubbles that form when you draw back on the plunger "too much" are not air that gets past the plunger (it forms a very tight seal), but cavitation bubbles: little areas of vacuum created by the low pressure

Hmmm. I'm open to that idea, though I wonder why the syringe then never fills? Perhaps the pressure is low enough that the alcohol (BA) is boiling to vapor and thus filling the syringe? I see the bubbles form around the plunger itself...I'll have to play more and see. I suppose I could try quickly drawing some olive oil. No BA in it, so eliminate the small alcohol from the equation. I'll play and post more.

When I first started, I'd draw too fast, see the bubbles around the plunger and end up injecting the air back into the vial to get rid of it. It sure SEEMED it was coming around the plunger. And the design of the plunger is such that the hard seal occurs under pressure, not under vacuum.
 
Doesn't the needle dull when you push it through the rubber seal on the bottle?

If it does, it isn't enough to matter. The 31g needle is so tiny to begin with, that I almost never feel it pierce the skin. This is certainly what occurs millions of times a day when diabetics take insulin. They draw and inject with the same needles I do, and I've never heard of one complaining that it's dull.

To be fair, I've never stuck myself with a totally unused needle...but now I probably will just to compare because I'm curious.
 
It dulls, but not a ton. When I was going into the test rubber top, then into the HCG rubber top, I could tell the difference. Just one top though - not really.

-Jim
 
Hmmm. I'm open to that idea, though I wonder why the syringe then never fills? Perhaps the pressure is low enough that the alcohol (BA) is boiling to vapor and thus filling the syringe? I see the bubbles form around the plunger itself...I'll have to play more and see. I suppose I could try quickly drawing some olive oil. No BA in it, so eliminate the small alcohol from the equation. I'll play and post more.

When I first started, I'd draw too fast, see the bubbles around the plunger and end up injecting the air back into the vial to get rid of it. It sure SEEMED it was coming around the plunger. And the design of the plunger is such that the hard seal occurs under pressure, not under vacuum.

The syringe should still fill (it does when I do this), it just may not be that obvious. Cavitation bubbles need a surface on which to nucleate, that's why you see them forming on the plunger and the walls of the syringe.

The plunger seal isn't directional, and pulling a vacuum is not more than a 15psi differential at sea level. I'm sure the plunger seal can withstand several (many?) times that in compression.
 
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