Overnight Glucose Testing: Who Does It and Why?

Do you wake up during the witching hour to test your blood sugar?

If you’re raising your hand, you’re probably the parent of a child with diabetes. But the odds are pretty slim that you’ll find an adult who willingly sets an alarm to test their blood sugar in the middle of the night, breaking peaceful dreams for a dose of reality. Sleep is supposed to be our break, our meager vacation from the struggles and stress of managing diabetes. Right…?

I’ll be the first to admit that I don’t test my blood sugar in the middle of the night. If I happen to be awake and I feel low, guess what? I’m low! I don’t need to fiddle around with a glucose meter to prove it. (Although it might help with that erroneous 30-day average.)

I’ve heard so many stories on Facebook and at diabetes conferences of parents who faithfully wake up every night — sometimes twice or more! — to check their child’s blood sugar, and beat themselves up if they happen to forget. I think, those poor moms and dads! All that lost sleep! It will be great when their child is old enough to wake up on their own and manage their own blood sugars, which is what I did once I reached middle school age. I always wake up from my low blood sugars now, I think happily. No need for alarm clocks here!

Or is there…?

The fact is, about 75% of the time, you’re going to sleep through a nocturnal low rather than waking up. Surprising, huh? Most of us probably think that if we don’t wake up, we didn’t go low. But the feeling of being low — caused by the release of epinephrine — is blunted when we’re sleeping, though sometimes it’ll kick in strong enough that it’ll jolt us awake.

In a totally unofficial survey of PWDs on Facebook, the majority of folks responding to my query said they don’t test their blood sugar at night because they “always” wake up. Well, that might be one of the biggest misconceptions type 1s have about their own disease!

Sadly, we regularly hear stories of PWD kids, teens and adults who pass away in their sleep. No one is sure what causes this dead-in-bed syndrome, but the theory is that a nighttime low blood sugar — called a nocturnal low — episode triggers some kind of fatal cardiac arrhythmia. Some studies estimate that “dead-in-bed” accounts for 6% of deaths in type 1 PWDs under 40.

In addition, there’s also been more data coming out of centers conducting in-patient trials of the Artificial Pancreas showing that many type 1 PWDs do have nocturnal hypoglycemia quite often, and it lasts a looong time without the PWD ever waking up. A JDRF study of adults and children showed their blood sugar was low for more than 2 hours a quarter of the time overnight! It’s the entire reason why the Medtronic VEO, with its automatic low glucose shut-off, is being vigorously fought over with the FDA.

“We’ve now known for decades that (overnight) is the most common time for severe hypoglycemia,” says Dr. Irl Hirsch, assistant professor and endocrinologist at the University of Washington, and a type 1 PWD himself. “Dead-in-bed syndrome is clearly related to this. We also showed in our JDRF CGM study nocturnal hypoglycemia is our main clinical problem.”

How do we naturally recover from a low blood sugar? Researchers aren’t entirely sure, because as you can imagine, it isn’t ethical to not treat someone having a low blood sugar just to study their reaction! But the theory is that our bodies are still able to naturally bring our blood sugar back up, despite the fact that diabetes severely limits our body’s counter-regulatory hormones, like glucagon.

Of course, there are some PWDs who test their blood sugar at night religiously, including team members here at the ‘Mine: Amy says she gets up every night to pee and so she regularly checks her glucose during that sleep break. And Mike says he actually does make a habit of setting an alarm to get up for a check in those instances when he’s running higher at bedtime and taking a bolus that could drop him down unexpectedly in the 3-4 a.m. range. He also does that when tweaking his basals.

Sysy Morales, a 29-year-old type 1 PWD in Virginia, who works as a health coach and blogger at The Girl’s Guide to Diabetes, says she tests regularly at night because “because we sleep for such a large portion of our lives and I feel if I can have decent blood sugar management for that portion, I feel more comfortable about my having diabetes long-term.”

“It’s scary to think about what time can do.  Testing before bed and testing a few times a week in the middle of the night for great blood sugars at night is a small price to pay for a huge gain,” she adds.

So true!

Maybe there’s not enough data to identify a trend in the adult type 1 community, but it seems that practices differ and many don’t get up to test with the diligence that parents do.

When I was sharing my musings on this topic with my husband, he responded, “Diabetes doesn’t stop existing when you go to sleep.”

Correct! We are asleep 1/3 of the day, and we know that our diabetes management doesn’t just settle into a “normal” range while we’re sleeping and only wreck havoc when we’re awake. Up until a few years ago, when the continuous glucose monitor came out, we had no idea just how much fluctuation can happen. But now that we’re more clued in, what are we going to do about it?

But waking up every night to do fingerstick tests of our blood sugars might not be the ideal course of action. And who here enjoys interrupted sleep, really?

Gary Scheiner, famous Certified Diabetes Educator and fellow type 1 PWD, says it’s important to find a balance between optimal safety and reasonable quality of life. That can be just as important for our health as testing our blood sugars. (Uh-huh!) Gary and Dr. Hirsch both believe that use of CGMs should be incorporated more often into PWDs management in particular for overnight monitoring, and Dr. Hirsch says he finds it counter-intuitive that physicians don’t recommend them more often.

CGMs aren’t exactly perfect, but Gary says that despite the imperfections, “CGMs make it much safer to sleep through the night without having to get up to fingerstick.” While many people struggle to use them because of false readings (either failing to alert, or alerting unnecessarily), for many people they are better than nothing. The more frequently a person has hypoglycemia, the more likely they are to be hypoglycemia unaware, which will affect you during the waking hours too.

Dr. Hirsch says, “I’m hoping that the promised improvement and hopefully better insurance reimbursement of CGM will both bring this problem better to the forefront but also decrease the frequency (of overnight hypoglycemia) in many patients.”

Image: 350.org

There is also the issue of hyperglycemia (high blood sugar), which is not as dangerous in the short-term, but can lead to an elevated A1c and later on, complications. Elevated blood sugar over a six-to-eight hour period will definitely have an impact on A1C if it happens regularly.

“I would argue that most patients with type 1 diabetes would benefit from an occasional overnight test, and obviously should test if there is a problem/need for adjustment in overnight insulin,” says Dr. Anne Peters, endocrinologist at University of Southern California’s Clinical Diabetes Program. “And I am a huge advocate for ever more accurate sensors.”

Although there is a connection between dead-in-bed and nocturnal hypoglycemia, Dr. Peters says it’s unlikely that a single middle-of-the-night blood sugar reading could save someone. “Dead-in-bed is something much more complex.  There are examples of patients dying in the middle of the night in spite of a functioning sensor.”

Gary also added that one additional check at night doesn’t necessarily guarantee you’ll always catch an asymptomatic low blood sugar, but it does give an additional opportunity to correct a pending problem.

Dead-in-bed might be a bigger medical mystery, but nocturnal hypoglycemia can still lead to seizures and comas, so it’s still something to be avoided! Plus, nocturnal lows can also cause nightmares, headaches, fatigue and mood swings, plus the added risk for hypoglycemia unawareness.

One thing you can cross of your list: the Somogyi effect. For years, doctors stated that the morning highs that PWDs suffered post-low was because of the body’s attempt to recover from a low blood sugar. But no one has ever been able to prove that happens, and now some researchers are saying that the highs after a low are really just from overtreating the low. CGM studies are also showing that there really are not consistent associated morning highs with low blood sugar. If you do have a morning high, it’s more likely from the dawn phenomenon.

It definitely seems there is a trade-off between testing overnight and choosing not to do so. While it can give peace of mind to some people, the snapshot of blood sugars that a fingerstick reading gives you is really no substitute for the movie that a CGM provides. But anecdotally, it seems that sensors only work accurately part of the time, and their respective alarms sometimes fail to wake a person when it does go off! What’s a PWD to do?

I suspect that it would help my own diabetes management if I tested more frequently in the middle of the night — even if only when I knew that something wonky had happened earlier in the day, like a big meal or unusual exercise. My fortune-teller skills are a bit rusty, and I sometimes have a hard time predicting what my blood sugars will do if I change up my usual routine. I might not need to test every night, but overall I think more frequent night time testing would alert me to fluctuations that cause chaos to my quarterly A1C.

So tell us, Dear Readers, do you test between bedtime and breakfast?