A few weeks ago I had breakfast with Jessica Apple at a cafe near Bryant Park in New York City. I perused the menu and was tempted by the list of carby desserts masquerading as “brunch.” Nevertheless, I ordered the quiche. Jess did too. I was in good company.
I was ready to test my blood sugar and bolus. But after riding the subway and handling menus, I was desperate to clean my hands before pricking my finger. I guess you could call me a germaphobic diabetic. Not the most charming description, but I’ll take it.
Invisible germs scare me. That is why I avoid public restrooms. Of course, that’s where most restaurants keep the soap and water, but I always feel dirtier on my way out of the restroom than I did when I walked in. Even if the faucet has an automatic sensor, I still have to touch the door handle when I exit. I know the tricks. Hold it with a paper towel. Pry it open with your shoe. Wait for a fearless person who scoffs at germs to hold the door for you. But still.
Thankfully I had packed hand sanitizer in my bag. No need to plan a restroom escape. I pulled it out and squirted a few drops onto my hands. I offered a squeeze to Jess and she happily cleaned her hands, too.
I went on to test my blood sugar. It’s always a treat to dine with other people with diabetes (especially germ-conscious ones). You don’t have to prick your finger under the table, or even worse, in the dirty bathroom. And you don’t have to explain your food choices.
After lathering up the hand sanitizer, Jess had an interesting thought: she wondered if the hand sanitizer could impact blood glucose readings. It was a great question that I never considered.
I decided to find out.
Over the course of a week, I completed ten back-to-back blood sugar tests to see if hand sanitizer affected the result. The first test was always done with no hand washing, no hand cream, no nothing. Then I applied hand sanitizer (a household name brand) immediately after testing. I waited a few seconds, tested again on the same finger and compared the two readings.
I found that no two blood sugar readings were ever the same. Seven readings were higher post-sanitizer, and three were lower. Eight out of ten test sets fell within 10% of one another. The largest difference between two tests was 12 points and 11.86%, respectively.
Interesting. But I didn’t feel closer to understanding the relationship between hand sanitizer and blood sugar readings.
I decided to do a second round of testing, but with a different type of hand sanitizer. In my next experiment, I used a generic pharmacy brand with added aloe.
Again my blood sugars skipped around. Five readings were higher post-sanitizer, four were lower, and one reflected no change (a miracle?). The results were a little wackier than in the first experiment, with five out of ten test sets showing a greater than 10% difference between the initial and post test. But without a pattern, I was still puzzled.
I did some research on the topic and came across this study published in the Journal of Diabetes Science and Technology: The Effect of an Instant Hand Sanitizer on Blood Glucose Monitoring Results.
It says: “Mean blood glucose values from fingers cleaned with instant hand sanitizer did not differ significantly from the control finger (p = .07 and .08, respectively) and resulted in 100% accurate results. . . .The data from in vitro experiments showed that the hand sanitizer did not adversely affect glucose meter results, but when an exogenous glucose interference [cola] was present, the effectiveness of the hand sanitizer on glucose bias (range: 6% to 212%) depended on the surface area and degree of dilution.”
Hmm. Exogenous glucose interference. Surface area. Degree of dilution. I didn’t account for those things.
I am no scientist, but after my finger-poking adventures, I hypothesized that blood sugar readings likely fluctuate even without introducing a variable. In order to find out if that were true, I completed another round of back-to-back testing, but without hand sanitizer. I simply tested. Waited a few seconds. Then tested again on the same finger.
My findings: five readings were higher in the second test, and five were lower. Like the first experiment, eight out ten test-sets fell within 10% of one another. The largest difference between two tests was 37 points and 14.57%. (One reading showed a 120 point jump – an 89.55% difference. But I am calling that degree of dilution.)
So what have we learned?
One thing is clear: if you perform back-to-back blood sugar tests, it is likely that the second blood sugar reading will be different than the first. Hand sanitizer or not.
While many of the percentage differences in my experiment were small – less than 10%– there were enough cases to make you scratch your head.
How does one accurately treat a high or low if the results are skewed? Even 10% can be significant when it comes to matters of blood sugar.
What if 180 was really 198? Or 162?
What if 80 was really 72?
And in the cases where the percentage differences were great, what if 40 was the new 30?
You get the idea.
In further research, I found an interesting article about meter accuracy by Riva Greenberg. She said, “Home meters have to rely mostly on their test strips for accuracy. Strips are easily affected by variation in manufacturing, temperature, climate, altitude and freshness (age). Also, substances in our blood like medication (something as simple as Tylenol), and/or our own red blood cells can interfere with our glucose reading.”
There she was explaining why home testing results are different than those done in the lab. But still, she brings up important points about the variations in the test strips. Something I hadn’t considered in my DIY experiment.
In the end, I feel disappointed in my meter, my test strips, and even my hand sanitizer. It’s all fallible and there’s not much I can do about it.
On the flip side, I’m thankful I can at least get a numerical reading. It wasn’t too long ago that people with diabetes were peeing on strips, only to get a vague range of where their blood sugar might be.
I think the lesson here is simply for us to be even more vigilant – more aware – of blood sugar variables. We already know that almost anything can affect our blood sugar levels. I guess a lot can affect the readings, too. Hand sanitizer isn’t the only suspect. There’s hand lotion. Nail polish remover. Crayon wax. The brand of your meter. Even the whim of your test strip.
From now on, if I’m feeling low, but my meter says 85, maybe I’ll test another few times to find out for sure. And if I’m feeling high and my meter says 120, instead of thinking, Hey, I got away with that!, I’ll prick my finger once more.
Sore fingers. The least of our worries.
In case you’re interested, here is my data. Disclaimer: I haven’t done math in a while.
*Art by Jennifer Jacobs