Diabetes Simplified: Polar Extremes
Blood sugar highs and lows in type 2 diabetes
By Wil Dubois
We often talk about blood sugar targets. How if you're above target you are too high, if you're below target you are too low. But what are the human limits? How high is it possible to go? And what happens to you up there? And what about lows? Can your blood sugar drop to zero? And if it did, what would happen to you then? And what causes the stupid highs and lows in the first place??
Simple. Diabetes causes high blood sugar. Diabetes medicines cause low blood sugar.
How highs happen
Diabetes interferes with the body's natural sugar regulation systems. In a nutshell, type 2 diabetes is a disease of insulin resistance. The body doesn't use its insulin smartly, so it has to make more. Eventually, the cells in the body that make insulin get so worn out from overwork that they start to burn out, and insulin production falls below the level needed to keep the blood sugar in check. Then like an elevator, blood sugars go up… up… up… up! Plus, these highs can be made worse by your own behavior, like drinking sugar-laden sodas that pack more punch than diabetes medicines can handle. Or being erratic in taking your meds. Or ignoring low-grade infections like gum disease. Diabetes causes high blood sugar, but it's sometimes the diabetic that fuels the fire.
How lows happen
To try to keep our blood sugar in check, we have an arsenal of medications to choose from. The problem is that blood sugar control is a game of averages, and life is not average. Life isn't consistent from day to day, and how we eat and how we move varies—as do our daily stressors. Food, exercise, and stress are the three largest movers and shakers in blood sugar, driving it either up or down. The perfect amount of medication for the sugar load on one day might be an overdose the next. And an overdose of blood sugar-lowering meds causes a low blood sugar.
The top of the mountain
How high can blood sugar actually go? Well, the all-time record high measured by a hospital (and in the Guinness Book of Word Records, no less) was 2,656 mg/dL (0.11 mmol/L). No, that's not a misprint. There really are four digits in that number. Luckily, four-digit blood sugars are exceedingly rare. But toxically high blood sugars are not. And how high would that be?
Lower than you'd expect.
For background, most home glucometers cap out at 600 mg/dL (33.33 mmol/L) and only read "Hi," indicating that blood sugar is higher than that. It could be 601 mg/dL (33.39 mmol/L) it could be 800 mg/dL (44.44 mmol/L), it could be 2,656 mg/dL. Who knows? But this almost never happens, you say, right? Wrong. You'd be surprised how often I see friendly blood sugar meters that welcome me with "Hi" when my patients drop in for a visit.
But won't blood sugars that high kill you? Yes. Absolutely. But it's a very slow process. Now, if a person with type 1 diabetes, like me, has very high blood sugars for any period of time at all he or she will go into a coma—and without medical treatment—will die. This can happen in as little as a day or two. But by comparison, type 2s rarely go into comas. It's possible for a type 2 to walk around with stratospheric blood sugars for weeks, months, or even years before succumbing.
This is actually not a blessing.
The problem is, while you aren't going to go into a coma, the sugars are slowly melting your body away. The damage from high blood sugar is slowly corrosive, like having a mild battery acid in your veins, slowly eating away at everything. At an A1C level of 9, blood sugar is considered toxic and long-time life threatening. Kidney damage is likely. Blindness is possible. Amputations are a real risk. But, because in type 2s, the damage to the body from elevated blood sugars is a slow process with no symptoms early on, it's not uncommon for type 2s to have been running blood sugars in the 350-400 range when diagnosed. If we were talking about drinking and driving—not diabetes—we'd be looking at numbers that are double the legal limit.
That A1C of 9 that marks the borderline between health and complications translates into an average meter reading of only 212 mg/dL (11.78 mmol/L). So you can see that if you are having blood sugars in the 600s, and tissue damage starts at 200, you have serious problem.
The bottom of the valley
At the other end of the diabetes spectrum, most home glucometers have a lower limit of 20 mg/dL (1.11 mmol/L), where they say "Lo." But in reality no one has ever gone that low and survived. Even in a hospital, mid-20s are fatal. Of course, you can always find someone who claims to have seen a 20 and lived to tell the tale, but the truth is that the meters are pathetically inaccurate at that level. No doubt these people were frighteningly low, but not that low. Of course a fatal low in a type 2 would require a massive overdose of diabetes medications, as once a low starts the T2's liver will release its emergency sugar supplies. Any bad low is a scary experience, but fatal lows in type 2s are rare.
Lows in the 30s are seen more frequently, and in medical jargon, these are called "officially scary." No, wait, that's not medical jargon. That's how I see them! Blood sugars in the 30s carry a real risk of causing a blackout, and if you go lights-out, at a minimum you could be injured by falling, and if you are by yourself, you won't be able to ingest fast-acting glucose to reverse the low, resulting in a longer period of unconsciousness.
Low 40s and 50s are more common, and in some people this is low enough that there's a risk of losing consciousness.
Lows in the 60s and 70s generally generate the cables-in-the-elevator-just-snapped sensation of a low blood sugar, but are not inherently dangerous. Still, lows of any kind are to be avoided as there's evidence that frequent lows can lead to brain damage, and in the elderly there's a risk that lows can trigger heart attacks in people with heart disease.
Walking the tightrope
So how high can you go? 400, 600, 800, a thousand. The sky's the limit, really. But above 200 for any time at all is high enough; high enough to kindle the fires of long-term diabetes damage. You might "feel fine" at 278 mg/dL (15.44 mmol/L), but you're not fine. Your cells know better, even when you don't.
How low can you go? 40, 32, maybe into the 20s. But unlike highs, there's a hard limit on the bottom end that ends in sudden death. And while there's no risk in being in the 70s and 80s, there's also no benefit.
Keeping your sugar in the target ranges is difficult. It's hard work. But the targets exist for a reason. So the question isn't really how high or low can you go? It's how high or low do you dare go? And the answer to that question is not very far at all.
Wil Dubois is the author of four multi-award-winning books about diabetes. He is a PWD type 1, and is the diabetes coordinator for a rural non-profit clinic. Visit his blog, LifeAfterDX.
NOTE: The information is not intended to be a replacement or substitute for consultation with a qualified medical professional or for professional medical advice related to diabetes or another medical condition. Please contact your physician or medical professional with any questions and concerns about your medical condition.
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