High blood sugar, known as hyperglycemia, can cause confusion and changes in mental status. Hyperglycemia occurs when glucose levels rise above the target range, often defined as above 180 mg/dL. Confusion signals the body’s struggle to cope with excess sugar and requires prompt medical attention.
How High Blood Sugar Affects Cognitive Function
Elevated glucose levels create an osmotic effect, the primary mechanism leading to cognitive impairment. The high concentration of sugar pulls fluid out of the body’s cells, including brain cells, causing cellular dehydration. This fluid shift directly impacts brain function.
Dehydration disrupts normal electrical signaling between neurons. Brain cells rely on a delicate balance of water and electrolytes, and this imbalance manifests as difficulty concentrating, sluggishness, and confusion.
The loss of fluid can also lead to electrolyte abnormalities, further impairing nerve conduction and mental processing. Acute confusion relates directly to these immediate osmotic and dehydration effects. Sustained high blood sugar can also cause long-term cognitive issues.
Recognizing Severe Hyperglycemic Events
Confusion signals two severe metabolic crises: Diabetic Ketoacidosis (DKA) and Hyperosmolar Hyperglycemic State (HHS). Both arise from dangerously high blood sugar and require emergency intervention.
DKA typically affects people with type 1 diabetes due to a severe lack of insulin, forcing the body to burn fat and produce acidic ketones. This causes symptoms like nausea, vomiting, a fruity odor on the breath, and deep, rapid breathing (Kussmaul respirations).
HHS is more common in type 2 diabetes, involving extreme hyperglycemia (often exceeding 600 mg/dL) and profound dehydration without significant ketone production. Since HHS develops gradually, confusion or loss of consciousness may be the first severe symptom noticed.
Neurological symptoms are pronounced in HHS due to extreme hyperosmolarity and severe dehydration. Recognizing confusion alongside other symptoms, such as extreme thirst or frequent urination, should prompt immediate medical help.
Why Low Blood Sugar Also Causes Confusion
Low blood sugar (hypoglycemia) also causes confusion through a distinct physiological process. The brain relies almost exclusively on glucose for energy, demanding approximately half of the body’s total sugar supply.
When blood glucose drops too low (typically below 70 mg/dL), the brain is deprived of its primary fuel source. This glucose starvation is called neuroglycopenia, which rapidly leads to cognitive impairment.
Hypoglycemia causes confusion because the brain lacks the energy to power its neurons. Symptoms of neuroglycopenia include disorientation, slurred speech, difficulty concentrating, and uncharacteristic behavior.
The symptoms often come on very quickly; confusion can set in rapidly once levels drop below 54 mg/dL. This mechanism differs from hyperglycemia, which affects the brain through dehydration and electrolyte shifts. Distinguishing between the two requires checking blood glucose.
Immediate Steps When Cognitive Changes Occur
If someone experiences sudden confusion, disorientation, or slurred speech, especially if they have diabetes, the first step is to check their blood glucose level. This quick check determines if the confusion is due to high blood sugar (hyperglycemia) or low blood sugar (hypoglycemia). Do not delay, as treatment for the two conditions is opposite.
If the person is severely confused, unresponsive, or unable to safely swallow, immediately call for emergency services. Clearly state the current blood sugar reading and any existing medical conditions to the dispatcher. This information helps first responders begin appropriate treatment quickly.
If the person is conscious and the reading is very high, they may require assistance with prescribed insulin, but emergency services should still be notified if confusion is present. Never give food, drink, or oral glucose to a person who is unconscious or struggling to swallow, as this poses a serious risk of choking or aspiration.