Ketones are acids your body produces when it burns fat for energy instead of sugar. In diabetes, ketones become a concern when insulin levels drop too low, forcing your body to break down fat at a rapid, uncontrolled rate. Small amounts of ketones are normal, but when they build up in the blood, they can make it dangerously acidic, a condition called diabetic ketoacidosis (DKA).
Why Diabetes Causes Ketone Buildup
Your cells normally run on glucose, and insulin is the hormone that lets glucose into those cells. When insulin is missing or severely insufficient, glucose stays locked out of your cells even though it’s flooding your bloodstream. Your body, starving at the cellular level, switches to its backup fuel source: fat.
Low insulin activates an enzyme that rapidly breaks down fat stores, releasing fatty acids into your bloodstream. Those fatty acids travel to the liver, where they’re converted into three types of ketone bodies. In small amounts, ketones are a perfectly fine energy source. The problem in diabetes is one of volume and speed. Without insulin to regulate the process, fat breakdown accelerates far beyond what the body can safely use. Ketones accumulate faster than your kidneys can clear them, and because ketones are acidic, your blood pH drops. That shift toward acidity is what makes high ketones a medical emergency.
This process is most common in type 1 diabetes, where the body produces little to no insulin. But it can also happen in type 2 diabetes during severe illness, infection, or when certain medications alter the balance of hormones that regulate fat metabolism.
Blood Ketone Levels and What They Mean
If you test your blood ketones at home, the numbers fall into four risk categories:
- Below 0.6 mmol/L: Normal. No action needed.
- 0.6 to 1.5 mmol/L: Low to moderate DKA risk. Recheck in one to two hours and follow your sick day plan.
- 1.6 to 2.9 mmol/L: High DKA risk. Contact your healthcare provider promptly.
- Above 3.0 mmol/L: Very high DKA risk. This is an emergency.
Urine ketone strips are another option, though they’re less precise. They show results as negative, trace, small, moderate, or large. Blood ketone meters give a real-time number and are generally more reliable, especially because urine results can lag behind what’s actually happening in your bloodstream.
When to Test for Ketones
If you have type 1 diabetes, you should check ketones any time your blood sugar is above 13.9 mmol/L (about 250 mg/dL) and isn’t coming down within two hours. You should also test whenever you’re sick, even if your blood sugar looks fine. Illness, vomiting, diarrhea, and infections all raise the risk of ketone buildup because stress hormones counteract insulin.
Pregnancy changes the rules. During pregnancy, ketones can develop at lower blood sugar levels than usual. Testing is recommended if blood sugar rises above 10 mmol/L (about 180 mg/dL) without a clear reason, or any time you’re feeling unwell.
If your first test shows ketones in the 0.6 to 1.5 mmol/L range, recheck in one to two hours to see whether the level is rising or falling. A rising number means what you’re doing isn’t working, and you need to contact your provider.
Symptoms of Diabetic Ketoacidosis
DKA doesn’t typically hit all at once. Early signs overlap with general high blood sugar symptoms: intense thirst, frequent urination, and fatigue. As ketones climb higher, more distinct symptoms appear. Nausea, vomiting, and abdominal pain are common. Your breathing may become rapid and deep as your lungs try to compensate for the acid in your blood. One of the most recognizable signs is a fruity or acetone-like smell on the breath, caused by one of the ketone bodies being exhaled through the lungs.
Confusion and difficulty concentrating signal that DKA is becoming severe. At this point, blood chemistry is significantly disrupted, and the situation can deteriorate quickly without treatment. DKA develops over hours, not days, which is why catching ketones early through testing matters so much.
Common Triggers
The most frequent cause is simply not having enough insulin on board. A missed injection, an insulin pump malfunction, or a dose that’s too low for your current needs can all set the process in motion. Illness is another major trigger because infections and fevers cause your body to release stress hormones like cortisol and adrenaline, which directly oppose insulin and promote fat breakdown.
A less obvious trigger involves a class of diabetes medications called SGLT2 inhibitors, which work by causing your kidneys to flush out excess glucose through urine. These drugs can produce a deceptive situation called euglycemic DKA, where your blood sugar reads normal or only slightly elevated while ketones are climbing dangerously. The medications lower blood sugar so effectively that the ketone problem can go unnoticed. They also increase glucagon levels and promote fluid loss, both of which accelerate ketone production. If you take an SGLT2 inhibitor, be aware that normal blood sugar doesn’t guarantee you’re in the clear, especially during illness or after surgery.
Nutritional Ketosis Is Not the Same Thing
People following very low-carb or ketogenic diets also produce ketones, and this sometimes causes confusion. Nutritional ketosis and diabetic ketoacidosis sound similar but are fundamentally different situations. On a keto diet, a healthy pancreas still produces insulin. That insulin acts as a brake, keeping ketone production within a controlled range, typically below 3 mmol/L. Blood pH stays normal.
In DKA, that brake is gone. Without adequate insulin, nothing stops the liver from flooding the bloodstream with ketones, levels can soar far above 3 mmol/L, and blood becomes acidic enough to interfere with organ function. The distinction is really about whether your body has the insulin it needs to regulate the process. If you have diabetes and are considering a low-carb diet, that’s a conversation to have with your provider, because the line between safe ketosis and dangerous ketone levels requires careful monitoring.
What to Do When Ketones Are Elevated
Drinking fluids is the first and simplest step. Water helps your kidneys flush out both excess glucose and ketones. If your ketone level is in the low-to-moderate range and you have a sick day plan from your provider, follow it. This typically involves additional insulin, continued fluid intake, and rechecking levels every one to two hours.
If you find moderate or high ketones on more than one test, or if you’re vomiting and can’t keep fluids down, call your provider. Many DKA situations can be managed with phone guidance and adjusted insulin doses if caught early. But if you’re experiencing confusion, persistent vomiting, rapid breathing, or ketones above 3.0 mmol/L, that’s an emergency requiring immediate medical attention. DKA is treatable, but the window for safe at-home management narrows as ketone levels rise.