YANMD- Freestyle Libre and Insulin

October 4, 2018 9:44 AM

Really basic question that I haven't found an answer to by searching on the internet. I am now a cyborg. I have the wearable tech of the Freestyle Libre glucose monitor. I want to know if I can inject insulin into that same arm without impacting the results of my monitor. Anyone know? Thanks!
posted by Draccy to Health & Fitness (5 answers total)

I do not know, but my guess is that injecting close to where you read won't make a difference to the readings. My chain of reasoning:

You inject insulin into tissue. Insulin slowly leaks out of the tissue into the bloodstream. It travels around the body very quickly - your heart pumps your full volume of blood in about a minute - telling cells to use glucose. As cells use glucose, your blood glucose drops.

Glucose slowly leaks out of the bloodstream into the interstitial fluid, which is where the Libre reads it. (This is why the Libre gives results that are a few minutes out of date - you're not measuring blood directly.) The blood that's pumping past the spot where you're measuring is a mix of blood that was in all sorts of different parts of your body just a minute ago. This means that the glucose that's leaking into your interstitial fluid is going to be an average of blood glucose levels from all over your body, and that's what the Libre will measure.

As a result, I don't think that there are "local lows" near the site of an insulin injection. I could, however, be wrong. If I am wrong, I suspect that I'm only wrong in a tiny area around the site of injection; i.e. I wouldn't inject a millimeter or two away from the sensor.
posted by clawsoon at 12:47 PM on October 4, 2018

I think I would just call my doctor to ask about this one. My gut says that it should be fine, but my head says that I'm not qualified to answer this question.
posted by Anticipation Of A New Lover's Arrival, The at 1:38 PM on October 4, 2018

I also think it won't matter because the Freestyle monitor isn't measuring insulin levels, it's measuring blood glucose and as clawsoon explains, there isn't much of a mechanism for local effect given how the insulin and monitor operate in the body.

I'd also guess that if major variations were found during human trials, the monitor would have instructions to not inject into the same area where the monitor is located.
posted by quince at 2:04 PM on October 4, 2018 [1 favorite]

Best answer: My wife uses that monitor. Her response is 'No. That is not recommended.'
posted by Jessica Savitch's Coke Spoon at 4:54 PM on October 4, 2018

Call the manufacturer and ask, or speak to a diabetes nurse educator.
posted by pecanpies at 5:29 PM on October 4, 2018