The number of Koreans with diabetes or prediabetes has surpassed 17 million. According to the Korean Diabetes Association's recently published "Diabetes Fact Sheet 2026," about 5.65 million people aged 30 and older have diabetes. Including those with prediabetes, more than 17 million people need to pay attention to managing their blood sugar.
The problem is that diabetes is not a condition that ends with simply lowering blood sugar readings. Post-meal blood sugar can rise sharply even when fasting levels are normal, and blood sugar can still swing widely even when hemoglobin A1c — which reflects average blood sugar over the past two to three months — falls within the target range. If management slackens, complications can develop in the eyes, kidneys, heart and nerves, requiring a comprehensive approach that covers diet, exercise, weight and medication.
Professor Kim Byung-joon of the Division of Endocrinology and Metabolism at Gachon University Gil Medical Center, appearing on Seoul Economic Daily TV's "Now, the Expert" at 9 p.m. on the 24th, said patients should not be reassured by a single reading. "Blood sugar keeps moving throughout the day, so you cannot relax just because of one measurement," he said. "Fasting levels may look good while post-meal levels are high, so you need to look at the overall pattern of change."
HbA1c, the Key Target in Blood Sugar Control
Managing diabetes requires looking at fasting blood sugar, post-meal blood sugar and HbA1c together. Fasting blood sugar is measured after at least eight hours without food and is affected by the previous evening's meal and sleep. Post-meal blood sugar is generally measured two hours after a meal begins and varies with portion size, the type of food and physical activity afterward.
HbA1c indicates average blood sugar levels over the past two to three months. The Korean Diabetes Association sets blood sugar targets for patients with type 2 diabetes at 80 to 130 mg/dL for fasting levels, below 180 mg/dL two hours after a meal, and below 6.5% for HbA1c.
What matters is tailoring management to which reading is elevated. If post-meal blood sugar is high, patients should adjust portion sizes and carbohydrate intake and increase physical activity. If morning fasting blood sugar is high, they need to check for late-night eating or insufficient sleep. In some cases, insulin resistance increases glucose production in the liver overnight. Nor can patients relax simply because HbA1c has entered the target range, because blood sugar can still rise and fall sharply even when the average looks good.
"We still regard HbA1c as an important target for blood sugar control, but the recent trend is to also look at the highs and lows of blood sugar through continuous glucose monitors, including how much time is spent within the target range of 70 to 180 mg/dL," Kim said.
Fruit Can Spike Blood Sugar Too; Move After Meals
Many people try to cut out carbohydrates as soon as they are diagnosed with diabetes. But carbohydrates should be eaten in appropriate amounts, with adjustments to the type of food and the way it is eaten. Choosing multigrain rice, which is rich in dietary fiber, over white rice and eating vegetables or seasoned greens first helps slow the rise in blood sugar and control portion sizes.
Fruit is a problem for patients with diabetes, since even small amounts can push blood sugar up sharply. "You should not exceed about one paper cup's worth," Kim said. "That is only about 10 grapes or three to four strawberries." Habits such as eating a lot of fruit in place of a meal, or finishing a plate of fruit while watching television after dinner, warrant particular caution.
Exercise after meals is also recommended. Walking or moving lightly for 10 to 20 minutes around 30 to 60 minutes after a meal, when blood sugar is rising, can help reduce the size of the spike.
Patients with type 2 diabetes who are obese can expect improvements in blood sugar from losing just 5% to 8% of their body weight.
Diabetes Drugs Now Protect the Heart and Kidneys as Well
Diabetes treatments are evolving. In the past, the focus was on how much a drug lowered blood sugar. More recently, treatment choices also take into account protecting the heart and kidneys and reducing the risk of complications.
The leading examples are SGLT2 inhibitors and GLP-1 class drugs. SGLT2 inhibitors block the reabsorption of glucose in the kidneys and increase its excretion in urine, and they also reduce the risk of worsening heart failure and chronic kidney disease.
GLP-1 class drugs, well known as obesity medications, were originally diabetes drugs. They promote insulin secretion and suppress appetite, controlling both blood sugar and weight. Some have also been shown to lower the risk of cardiovascular disease.
Screen for Complications Early After Diagnosis
The ultimate goal of diabetes management is to prevent complications or delay their progression as much as possible. Major complications include diabetic retinopathy, diabetic kidney disease and neuropathy, and they can also lead to cardiovascular disease such as heart attack or stroke.
Because type 2 diabetes often begins several years before it is diagnosed, it is important to start screening for complications from the early stages after diagnosis.
Blood pressure and cholesterol must be managed alongside blood sugar. "Diabetes, high blood pressure and high cholesterol often appear together on a foundation of obesity," Kim said. "All of them damage blood vessels, so they have to be managed at the same time to reduce complications."
"Prediabetes is a stage where you can return to normal if you make the effort, so this window should not be missed," Kim said. "Even if diabetes or complications have already developed, consistent management can meaningfully delay progression to severe stages such as blindness, dialysis or cardiovascular disease."
