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
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.
This could have been the cause of your inconsistent readings. We are advised to always wash our hands and dry well before testing. That raspberry smoothie you had earlier could have just shown up in your test.
Your meter and test strips are only required to have +/- 20% accuracy to be approved by the FDA. If you want more details about the potential variations in your readings, you might be interested in the Blood Glucose Monitoring information at Diabetes Self-Management? http://www.diabetesselfmanagement.com/articles/Blood-Glucose-Monitoring/ Here’s a quote from Wil Dubois’ article: As of this writing, the standards for FDA approval of a meter and strip system are plus or minus 20% accuracy, 95% of the time (compared with a lab blood glucose test). This means that if your blood glucose level is 100 mg/dl, a meter and strip that… Read more »
The readings “dropped a point,” and that is cause for such alarm and “WTF” exclamations ?
Should be thanking the gods for such consistency of readings!
Very good article. It was definitely practical, particularly for “numbers” people like me. Thanks for the info,
Joanne, I’d gather that’s still within the range for the glucometer.
If you are dropping about 60 points per hour, it would make sense. Additionally, it’s within the range of the machine to have it within a few points – totally normal.
Thanks for this! I checked on it after I got a crazy high reading. Sure enough, I tested 3 more times within 3 minutes and the reading dropped by an entire point each time. WTF!?
Great article and notes on this issue. Hand sanitizer has been my ‘go-to’ while I’m on the go or while commuting (some bathrooms are gross out there!). I hadn’t put much thought into the potential results and assumed that it would probably be similar to alcohol swabs, which I don’t use – instead either old school soap and water or hand sanitizer. Thanks so much for testing out your theory for us, much appreciated. Recently I noticed that there was a difference in readings taken from the same finger (ring) on my left and right hands when testing within a… Read more »
Fabulous article! I’ve wondered about that! I’ve been hesitant to give my son hand sanitizer for fear that it would alter the BGs. Glad to know it’s not an issue. Yes, with great technological capabilities, accuracy could certainly be — and should be improved.
Your meter and test strips are only required to have +/- 20% accuracy to be approved by the FDA. If you want more details about the potential variations in your readings, you might be interested in the Blood Glucose Monitoring information at Diabetes Self-Management? http://www.diabetesselfmanagement.com/articles/Blood-Glucose-Monitoring/ Here’s a quote from Wil Dubois’ article: As of this writing, the standards for FDA approval of a meter and strip system are plus or minus 20% accuracy, 95% of the time (compared with a lab blood glucose test). This means that if your blood glucose level is 100 mg/dl, a meter and strip that… Read more »
The readings “dropped a point,” and that is cause for such alarm and “WTF” exclamations ?
Should be thanking the gods for such consistency of readings!