High blood sugar can cause various health problems. This article explains the reference values for blood glucose and HbA1c levels, complications of diabetes, risks of prediabetes, and the effects of hidden high blood sugar. It emphasizes the importance of early detection and preventive measures to avoid adverse effects on blood vessels.
Updated on 2025/02/27
Index
- Diabetes Diagnostic Criteria
- Diabetes and Its Effects
- Importance of Prediabetes (Borderline Diabetes)
- The Dangers of Hidden High Blood Sugar
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Diabetes Diagnostic Criteria
In Japan, diabetes is diagnosed based on the following two criteria.
- Fasting Blood GlucoseThis is the concentration of glucose in the blood when measured after not eating or drinking anything for at least 10 hours. This value helps evaluate how the body controls blood sugar in its normal state. The diagnostic criteria are shown in the table below.
Blood Glucose (mg/dL) | Below 100 | 100 to below 110 | 110 to below 126 | 126 or above |
Assessment | Normal | High-normal | Borderline | Diabetic |
- HbA1c (Hemoglobin A1c)This is a substance formed when blood pigment (hemoglobin) binds with glucose, serving as a long-term indicator that shows the average blood glucose levels over the past 1-2 months. It allows for more stable assessment as it is not affected by temporary blood glucose fluctuations. The diagnostic criteria are shown in the table below.
HbA1c | 5.5% or below | 5.6 to 5.9% | 6.0 to 6.4% | 6.5% or above |
Assessment | Normal | High-normal | Borderline or Diabetic | Diabetic |
Diabetes and Its Effects
Diabetes occurs when there is either a decrease in the secretion of insulin, a hormone that promotes glucose uptake from blood into tissues such as muscles, or when insulin's effectiveness decreases. This leads to chronically elevated blood sugar levels, which adversely affects various parts of the body.
When high blood sugar levels persist, blood vessels throughout the body gradually become damaged, potentially leading to various complications such as:
- Retinopathy: Damage to blood vessels in the retina of the eye, which can lead to vision loss or blindness
- Nephropathy: Decreased kidney function, which may eventually require dialysis
- Neuropathy: Symptoms such as numbness, pain, and sensory abnormalities in hands and feet
- Cardiovascular disease: Increased risk of heart attacks and strokes
If you have concerns about diabetes symptoms or test results, it's important to seek medical attention early.
Importance of Prediabetes (Borderline Diabetes)
Even if you haven't met the diagnostic criteria for diabetes, caution is needed when in the state called "borderline." Although there may be no obvious symptoms at this stage, changes are already beginning in the body.
Characteristics and precautions for borderline diabetes:
- When borderline conditions persist, the risk of progressing to diabetes increases significantly within a few years
- According to the Japanese Diabetes Society guidelines, the risk of atherosclerotic diseases (such as heart attacks and strokes) begins to increase even at the borderline stage
- Borderline diabetes is called a "silent state" and is often overlooked due to lack of symptoms, but changes are gradually progressing in the body
The Dangers of Hidden High Blood Sugar
While many people might think "This doesn't concern me because I don't have diabetes," even if you're diagnosed as "normal" in regular health checkups, you may unknowingly be experiencing "hidden high blood sugar" in your daily life.
Hidden high blood sugar and its effects:
- When "postprandial blood sugar spikes" repeatedly occur, temporarily exceeding the normal upper limit to around 140-180mg/dL, protein glycation is promoted each time, damaging cells
- The longer high blood sugar conditions persist, the more protein glycation progresses. Even with "mild hyperglycemia" that doesn't qualify as diabetes, if it continues chronically, tissue damage accumulates
- Even in healthy people, when blood sugar rises sharply after meals or remains slightly elevated, protein glycation can progress unknowingly, potentially increasing future health risks
The problem is that regular health checkups using fasting blood glucose tests make it difficult to detect this kind of post-meal "hidden high blood sugar." Therefore, methods that can continuously monitor blood glucose levels, such as Continuous Glucose Monitoring (CGM), are effective for understanding more detailed blood glucose fluctuations.
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