High blood sugar, medically known as hyperglycemia, can cause feelings of dizziness and lightheadedness. Hyperglycemia is defined as a blood glucose level that rises above the target range. This sensation of unsteadiness is a recognized symptom indicating elevated glucose levels needing attention.
How High Blood Sugar Leads to Dizziness
The primary mechanism linking elevated glucose to dizziness involves the body’s attempt to eliminate excess sugar. When blood glucose concentrations are too high, the kidneys filter and excrete the surplus sugar into the urine. This process, called osmotic diuresis, causes the kidneys to pull large amounts of water from the body’s tissues and bloodstream to flush out the glucose.
The resulting high volume of urination, known as polyuria, quickly leads to significant dehydration. As the body loses this excessive fluid, the overall blood volume decreases. A lower blood volume causes a drop in blood pressure (hypotension), which compromises circulation. Reduced blood flow to the brain due to this volume depletion results in lightheadedness or dizziness.
This compromised circulation means the brain is not receiving the steady supply of blood and oxygen required to function optimally. The dizziness is a direct physical consequence of the severe dehydration triggered by the body’s glucose-management response. Chronic hyperglycemia can also contribute to vascular issues, making blood vessels less responsive and further affecting the steady flow of blood throughout the body.
Other Warning Signs of Hyperglycemia
Dizziness rarely occurs in isolation when blood sugar is high; it is usually accompanied by other physical signs. The fluid loss mechanism that causes dizziness also triggers an intense need to drink, medically termed polydipsia, as the body attempts to replace lost water. This is paired with the frequent need to urinate (polyuria), which causes the dehydration.
Individuals experiencing hyperglycemia often report feeling unusually tired or fatigued, even after adequate rest. High glucose levels can also lead to temporary vision changes, most commonly blurred vision, as fluid shifts within the lens of the eye. A persistent headache is another common complaint that occurs alongside these symptoms.
Comparing High Sugar Dizziness and Low Sugar Dizziness
Dizziness can be a symptom of both hyperglycemia and the opposite condition, hypoglycemia (blood sugar below 70 mg/dL). Recognizing the surrounding symptoms is necessary because the treatments for the two are opposite. Dizziness from high blood sugar tends to have a slower, more gradual onset, developing over hours or days, and is closely tied to dehydration and overall malaise.
Dizziness caused by low blood sugar comes on much more suddenly and is often accompanied by distinct signs of the body’s stress response. These rapid-onset symptoms include inner shakiness, cold sweats, a fast heartbeat, and sometimes confusion or anxiety. The brain is starved of its primary fuel source in hypoglycemia, leading to a quick malfunction, unlike hyperglycemia where the issue is primarily circulation due to dehydration.
Immediate Steps When Feeling Dizzy
The immediate first step when experiencing dizziness is to ensure physical safety by sitting or lying down to prevent a fall. After securing a safe position, the next action is to check the current blood glucose level using a meter to determine the cause. This reading dictates the appropriate response, as treating high blood sugar with sugar will dangerously worsen the situation.
If the blood sugar reading is high, the immediate focus should be on gentle correction and hydration. It is important to drink water or other non-caloric, non-sugary fluids to combat the dehydration that is causing the dizziness. Individuals using insulin should follow their prescribed correction dose plan, and then continue to monitor their levels as the treatment takes effect.
Seek emergency medical care if dizziness is accompanied by signs of a severe hyperglycemic complication, such as diabetic ketoacidosis (DKA).
Warning Signs of DKA
Warning signs for DKA include:
- A fruity odor on the breath
- Persistent vomiting
- Severe confusion
- Shortness of breath
If a blood sugar reading is extremely high (above 240 mg/dL) and accompanied by any of these severe symptoms, contact emergency services.