Diabetic Ketoacidosis (DKA) is something we talk and hear about a lot as people living with diabetes, but I honestly didn’t fully understand it until med school.
Here's what it’s not:
- Just high blood sugar
- Just ketones
It’s not even high blood sugars and ketones! It’s a complex metabolic process that requires formal laboratory criteria to diagnose. It cannot be diagnosed based on signs, symptoms, or medical history.
Why Does DKA Occur?
DKA is caused by an absolute or relative deficiency of insulin, not high blood sugars.
Let me reiterate. Diabetic ketoacidosis is caused by one thing and one thing only: insulin deficiency. This is because insulin suppresses ketone production. Ketones aren’t inherently bad -- they are quite literally brain fuel. But without enough insulin to keep them in check, they run amok.
DKA can be a result of absolute insulin deficiency (a person with diabetes who doesn’t produce insulin and goes without it having any insulin in their system for hours or days) or relative insulin deficiency (a person with diabetes who does have some insulin in their system, but not enough to control ketone production).
But high blood sugar does not cause DKA. Of course, not getting enough insulin and high blood sugar often do go hand in hand. But we can go into DKA with normal or even low blood sugars. Specifically and most commonly, this happens when people have nausea, vomiting, and diarrhea, and are unable to keep food in their GI tract or can’t absorb what is in there well.
And when you can’t eat and/or are going low because of that, it can be super tempting to not give insulin to avoid lows. But you can go into DKA even with a low blood sugar if there is not enough insulin in your system.
The Science Behind the Insulin-DKA Connection
Insulin does a lot metabolically, including suppressing fat breakdown.
Fat breakdown produces ketones (like beta hydroxybutyrate, or BHB). Not enough insulin gives way to too many ketones. Ketones are acids, which drop pH.
Our blood lives at a nice, consistent pH of about 7.4. When we are deficient in insulin, ketones build up, making our blood more acidic (and making us feel gross). We have buffers in our blood (bicarbonate, or HCO3) that exist to maintain the body's natural acid-base (pH) balance. So HCO3 is low in DKA because we are using up all our natural resources.
And that only buys us time -- breathing is the fastest way to actually get rid of acid (both CO2 and ketones), so rapid breathing is a classic symptom of DKA.
Our blood also lives at a certain concentration. When we have excess glucose and/or ketones, it gets more concentrated, changing the way water and ions flow across cell membranes. When we have too much acid in our blood, this changes the balance of + and - ions, which also changes how ions flow across cell membranes.
This can cause cerebral edema, coma, and death, and dictates a lot of how DKA is treated. It’s not as simple as just giving insulin when someone is really, truly in a DKA state.
So, DKA causes an anion gap metabolic acidosis because there are more anions (ketoacids) than usual floating around, either because the body is producing too much of them or because the kidneys cannot remove them fast enough.
It also causes low bicarb and low pH because you are using up all that buffer for the acid. And obviously, you need to have high BHB, too (usually >4ish, but I’ve met some unimpressed by anything < 10). So to technically and absolutely diagnose DKA, you need:
- pH < 7.35
- bicarbonate < 18
- BHB > 4
All of these things must occur simultaneously to reach a state of DKA.
DKA Means There’s an Insulin Deficiency
Again, these values do not require high blood sugar. Euglycemic DKA happens (although, rarely)! And there are other types of ketoacidosis, too.
The final teaching point here (and worth a separate post): having ketones does not mean you are in DKA. All the above markers of anion gap metabolic acidosis must also be in effect for someone to truly be in a state of DKA. This is why when going keto (or low carb), you may have ketones present in your blood, but that doesn’t mean you’re in a state of DKA.
But again, at the root of DKA is insulin deficiency, whether that’s absolute or relative. That’s why it’s critical to make sure you understand how insulin works in your body! How do you do that? Check blood sugars, often!