Why Don't Insulin Needles "Damage" You or Hurt When Poking Yourself?

[kyphysics]

This week was my first week injecting insulin (I have Type 2 diabetes) after less successful treatment with oral meds.

I was always scared of this phase (if I ever got there) and thought it might hurt to stick myself with an injection needle. However, I was pleasantly surprised. There was practically zero feeling (other than the tiniest of tiny prick/pinch feelings) when I stuck the needle in my belly. After the needle was completely inside me, I pressed the pump and that didn't hurt either. The whole process was rather non-eventful (pain-wise).

This is different from blood lab work procedures, where they stick a needle inside a vein to draw out tubes of blood. I've been pricked many times in a painful way and the latest (last week) was actually a bit painful. The lab person told me to drink more water next time to make it easier.

So, here are some questions:
a.) Why does the insulin needle not hurt, whereas the blood draw needling hurt? Is it due to the size, location, and method of injection?

I did notice my insulin pen having a VERY thin needle (it's so thin you can barely see it if not up close to it). So, I surmised it was partially size/thickness. And, of course, I'm also sticking it into my belly (which has lots of fat) vs. that elbow crease area where blood draws are common.
Does having more body fat make it less painful?

b.) Why don't suck needles "damage" our body when poking it into us. This may seem like a dumb question, but consider if I took a screw driver or knife and shoved it into my belly in the exact same area that I'd probably end up going to the hospital for serious damage. I cannot just stab myself with a sharp big object without hurting myself.

Is it just that the insulin needle is so thin that it can really "tear" much? It guess it's weird, b/c I figure conceptually any time you stick something inside you that it's going to be "damaging" something (at bare min. piercing your skin cells).

In theory, COULD an insulin needle damage you? Or, is it literally so thin that it's not going to damage you in any meaningful way (vs. a knife) when inserted?

 

[berkeman]

Insulin injections are generally done sub-q:

https://medlineplus.gov/ency/patientinstructions/000430.htm

So as long as you clean the injection site with an alcohol swab (were you taught how to do that?), you should not get an infection from the injection.

Since the injection is sub-q, you can lesson the pain of the injection by pre-squeezing the injection skin area -- that temporarily lowers the ability of the pain receptors to transmit any pain reaction.

 

[berkeman]

a.) Why does the insulin needle not hurt, whereas the blood draw needling hurt? Is it due to the size, location, and method of injection?

Probably it's due mostly to the size of the needle. You can ask the phlebotemist next time what gauge needle they are using, and you might be able to request a smaller gauge needle for the blood draw, depending on how much blood they need and how much time they have to sit there.

Edit/Add -- LOL, my wife always asks for a smaller needle when she's getting blood drawn.

 

[kyphysics]

Insulin injections are generally done sub-q:

https://medlineplus.gov/ency/patientinstructions/000430.htm

So as long as you clean the injection site with an alcohol swab (were you taught how to do that?), you should not get an infection from the injection.

Yup - wipe down with rubbing alcohol.

 

[jim mcnamara]

Density of sensory neurons varies by location in the skin. The tip of your forefinger has a high density, the middle of the abdomen a lower density.

An extreme example:
sharpen several pencils. Place either 1,or 2, or maybe 3 pencils into a group (like a column). Make sure the tip(s) are co-planar. (1 point is automatically good to go).

Lightly touch the nape of an assistant's neck with the pencil group. Ask how many pencils? Repeat this several times with 1, 2, or 3.

The density of sensory neurons in the back of the neck is quite low, so the assistant cannot accurate feel the number of points and is likely guessing. I once botched this in an anatomy class. The student "pokee" could see herself in a mirror. Her neurons were perfect. For a short while. Another student ratted on her. So that was fun....

 

[DaveC426913]

There's a big difference to injecting things sub-cutaneously, because you aren't constrained by where it needs to go. So you have the luxury of picking a place where it won't hurt. My needles (Trulicity) are injected into the fatty tissue around my belly. Not a lot of nerves there.

The needles do a bit of damage, but because it's not right into a large vein, there's very little bleeding. And these needles are both thin and sharp enough**, not only do they not hit blood vessels, but the wound easily gets squeezed shut and heals. Still, they do suggest you switch up where you inject.

** chefs know that (given your druthers) it's better to cut yourself with a sharp knife than a dull one. A sharp cut does much less damage than a dull one, which mangles the skin in a way that it can't knit back together easily.My pen automatically swabs the injection site with alcohol. A marvel of engineering.

 

[Averagesupernova]

I have had very few blood draws that I consider painful. Feels like a mosquito bite usually. Only time I've had it slightly painful was after fasting. Was told not to drink anything either. So, a teeny bit dehydrated. As it turned out, water would have been fine, but there was a miscommunication so I hadn't anything to drink for 12 hours.

 

[Tom.G]

request a smaller gauge needle for the blood draw

I second that! For many years I had 2 to 4 blood draws a year without anything more than a tiny prick sensation; the it started feeling like the needle was stretching the blood vessel. Un-comfy!

I switched arms for the draws and that helped for a few years, then the 'stretched blood vessel' sensation returned.

Now I always ask for a kiddie (child) sized needle and it's mostly back to the 'tiny prick' sensation.

Certainly worth a try!

Cheers,
Tom

 

[DaveC426913]

When it comes to blood draw, I have only one bit of advice:

If they don't hit a vein, they start again. They do not dig around looking for the vein. That will leave your veins chopped up like yesterday's dinner.

If you see them doing this, request a different attendant, as this one needs to be retrained.

 

[Bystander]

https://www.google.com/search?q=but...NDY5NzFqMGo3qAIAsAIA&sourceid=chrome&ie=UTF-8

 

[kyphysics]

Density of sensory neurons varies by location in the skin. The tip of your forefinger has a high density, the middle of the abdomen a lower density.

That makes sense for answer the pain question.

As for the damage part, it's still weird that we don't just "damage" something significantly or in a way that squirts more blood when doing an insulin injection. I've been pricked by a staple edge and bled. With the needle, it goes completely into my stomach.

But, the needle really does seem much, much more thin than a staple.

 

[hutchphd]

I know that for long term (typically type 1) diabetics the injection sites tend to slowly "toughen up" a little and that can change the perfusion rate of the insulin. I do not know if this is from the needle or the repeated insulin exposure. This makes much less difference for type 2 patients using long acting insulin.
I often use scalpels for high quality fine trimming of prototypes etc. Occasionally I will slightly cut myself and be totally oblivious to the event until I notice blood! They are also amazingly sharp. Cheap, too. Store them safely!

 

[kyphysics]

I often use scalpels for high quality fine trimming of prototypes etc. Occasionally I will slightly cut myself and be totally oblivious to the event until I notice blood! They are also amazingly sharp. Cheap, too. Store them safely!

Interesting. For some reason, this made me think of a totally separate bodily tear with bullets.

I've always heard that people don't really feel or know they've been shot oftentimes until the bullet cools down. Then, it is excruciatingly painful. But for a time, many people don't feel much of anything. That's another weird one, given how big a bullet can be.

 

[hutchphd]

The scalpel incidents, if simple and treated immediately, are usually healed in a day. Would that were true of bullets. I don't think they are similar.

 

[kyphysics]

The scalpel incidents, if simple and treated immediately, are usually healed in a day. Would that were true of bullets. I don't think they are similar.

Obviously, not. Bullets are larger and will tear you up inside.

So, if the scalpel wound heals so quickly, do we attribute that to how thin/sharp the object was?

Although, that cannot account for everything. Location has to matter too. If I slit someone's throat with a scalpel, that surely is different from slitting their belly fat, no?

In the same way, if I stick myself with an insulin injection needle in the eye-ball, I'm guessing I'll have much more pain and a hard time healing vs. that same needle in my belly or upper-arm (both typical injection sites).

 

[hutchphd]

I will speculate that both the scalpel and and the fine gauge needles are slippery enough to push the cutaneous (and sub cutaneous fat) cells apart doing little damage to the cells and their support. I think veins (and probably eyeballs) and more tightly constrained cell-to-cell.
Probably neither needles nor scalpels should be inserted into the eyeball routinely.

 

[DaveE]

The needles used for blood draws have to be large to avoid damage to the cell walls of the stuff they want to measure (hemolysis). The shear stress entering a tiny needle is too great for the strength of the cell membranes. OTOH, it's much harder to damage a protein like insulin and you don't have to inject much of it, so they can use skinny needles for that.

 

[tech99]

The scalpel incidents, if simple and treated immediately, are usually healed in a day. Would that were true of bullets. I don't think they are similar.

Called "healing in the first intention".

 

[kyphysics]

The needles used for blood draws have to be large to avoid damage to the cell walls of the stuff they want to measure (hemolysis). The shear stress entering a tiny needle is too great for the strength of the cell membranes. OTOH, it's much harder to damage a protein like insulin and you don't have to inject much of it, so they can use skinny needles for that.

That's interesting.

I would also think blood draw needles need to be a bit thicker to allow faster/easier sucking in of blood. Those insulin needs are ultra thin and would seem to take forever to do a multi-tube draw (esp., in an emergency situation).

All that being said, I'm starting to get "sore" in my belly from lots and lots of pokes recently. It's still minor, but it's "adding up." I do try to vary the injection spots - per the tip in this thread - but you can only vary so much on the belly. It adds up over time.

 

[DaveE]

I would also think blood draw needles need to be a bit thicker to allow faster/easier sucking in of blood. Those insulin needs are ultra thin and would seem to take forever to do a multi-tube draw (esp., in an emergency situation).

Yes. This is also true. Flow rate and viscosity are also a concern. For example, if you are nearly dying of dehydration and show up in an ER, they will use a fat needle to inject saline in asap, even though water and salts are tiny and can't be broken. If they put you on a bypass machine, they'll use really fat needles to move a lot of blood. Catheters, actually, in both cases.

 

[DaveC426913]

Yes. This is also true. Flow rate and viscosity are also a concern. For example, if you are nearly dying of dehydration and show up in an ER, they will use a fat needle to inject saline in asap,

Likewise, if you have just vomited up several litres of blood onto their shiny clean emergency room floor, they will insert one of these

into your femoral vein and pump you full of whole blood.

That leaves a mark; trust me.

 

[BillTre]

You can that a big catheter?
Here's a big catheter story.

A friend of mine had a big heart operation a few days ago.
I happened to be visiting him in the ICU when they were taking some big tubes out of him. One was sutured on to him the right side of his neck.
The nurse pulled out a large long catheter. It was a flexible soft plastic tube about 1 to 2 mm in diameter and about 4 to 6 inches long. It was threaded down to his aorta near his heart, in case they had to dump lots of blood into him during an emergency (they didn't).
The guy removing the tube just held some gauze on the hole for a few minutes and covered it with layers of gauze and bandage-like things. No blood got out.
I asked him how it was put in. At the beginning of the operation, an incision was made and the tube in was poked.

 

[hutchphd]

A thought for your friend's speedy recovery. Yikes!

 

[BillTre]

A thought for your friend's speedy recovery. Yikes!

He's actually doing quite well.

 

[DaveC426913]

The guy removing the tube just held some gauze on the hole for a few minutes and covered it with layers of gauze and bandage-like things. No blood got out.

Gadzooks, I assume they aimed for the jugular vein and not the carotid artery, otherwise they'd have a geyser.

 

[DaveE]

Gadzooks, I assume they aimed for the jugular vein and not the carotid artery, otherwise they'd have a geyser.

He's likely mistaken. Central lines are put in veins, not arteries.

 

[DaveC426913]

He's likely mistaken.

He didn't actually specify.

 

[BillTre]

The nurse told me the tube was going right to the aorta right above the heart (which is close to the neck site), thus it should be an artery.
However, the there was not spurting blood so maybe it was a vein, on the other hand he had good hand technique.
I was kind of surprised he could remove his hand pressure so soon.

 

[DaveE]

The nurse told me the tube was going right to the aorta right above the heart (which is close to the neck site), thus it should be an artery.
However, the there was not spurting blood so maybe it was a vein, on the other hand he had good hand technique.
I was kind of surprised he could remove his hand pressure so soon.

Probably the Superior Vena Cava, which is also right next to the heart. There is no need for blood delivery to have arterial access or to go into the aorta. It just doesn't make sense for them to do this.

 

[.Scott]

See figure 3a in Microneedle Systems and Apparatus

 

[berkeman]

See figure 3a in Microneedle Systems and Apparatus

Dat looks scary...

 

[.Scott]

Dat looks scary...

I am told it is unnoticeable.

 

[sophiecentaur]

I often use scalpels for high quality fine trimming of prototypes etc. Occasionally I will slightly cut myself and be totally oblivious to the event until I notice blood! They are also amazingly sharp.

It really is all down to sharpness. I remember having my jabs at school in the 50's and it certainly hurt. Those needles were all re-used (sterilised) but became blunt pretty quickly, I imagine. These days, all needles (certainly the thin ones) are single-use and I'd bet the manufacture has improved a lot over the years.
I'm only an amateur at self injection; just a short course of Clexane, post op but it really is surreal to stick a pointy thing into your tummy and squirt stuff in. But virtually no sensation at all.
Likewise when having blood samples taken with thicker needles the only discomfort is once the needle is actually in there and if the phlebo guy jiggles around a bit. The secret is always total relaxation and no fidgeting.

What's the state of 'air guns' for medication these days? They used one as a local anaesthetic for blood donors way back but it was useless - smashed the skin and made a blister sometimes.

BTW, great "when I was in the war, son" thread. I nearly passed it by.