Type 2 diabetes is often called a “silent killer” because many of its early warning signs are so subtle that they’re easy to dismiss. In some cases, the symptoms seem completely unrelated to blood sugar, making it unlikely that people will connect them to a metabolic problem. As a result, high blood sugar can quietly cause damage for years before a diagnosis is ever made.

In this article, we’ll first review three classic symptoms of high blood sugar, followed by ten lesser-known or unusual signs that may indicate your blood sugar has been elevated for far too long.

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Understanding Blood Sugar and Diabetes Risk

Diabetes and high blood sugar don’t appear overnight. Instead, they develop gradually along a spectrum. Ideally, daytime blood sugar levels should remain between 70 and 80 mg/dL, with an HbA1C below 5.5%.

Once blood sugar rises above this optimal range, the body enters a higher-risk state. Even mild, ongoing elevations can trigger long-term damage to blood vessels, nerves, and vital organs.

So-called “borderline” high blood sugar—often labeled as prediabetes—is defined by fasting glucose levels between 100–125 mg/dL and an HbA1C of 5.7–6.4%. This stage should not be taken lightly. Research shows that damage to the heart and blood vessels may already be occurring, even without a formal diabetes diagnosis. In fact, studies suggest that nearly two-thirds of heart attack patients admitted to emergency rooms had prediabetes beforehand.

In other words, the risk of heart attack and stroke increases with any sustained rise in blood sugar beyond the normal range—not just with full-blown diabetes.

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Three Common Symptoms of Type 2 Diabetes

1. Increased thirst and frequent urination

One of the most common early signs of high blood sugar is excessive thirst paired with frequent urination.

When glucose builds up in the bloodstream, the kidneys work harder to remove the excess sugar, leading to polyuria, or excessive urination. This fluid loss naturally triggers intense thirst and may also cause dizziness or lightheadedness.

Reaching for sugary drinks or fruit juice can worsen the problem by further raising blood sugar. While thirst and urination can be caused by many factors, frequent or persistent episodes may signal diabetes.

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2. Constant hunger

High blood sugar that is poorly regulated can lead to polyphagia, or excessive hunger. Blood sugar spikes followed by sharp drops may cause shakiness, irritability, and intense cravings—often referred to as “hanger.”

Many people respond by eating more carbohydrates or sweets, thinking this will fix the crash. Unfortunately, this only fuels the cycle of blood sugar instability. A more effective strategy is focusing on lower-carb foods, adequate protein, and healthy fats, which help stabilize glucose levels and reduce cravings.

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3. Ongoing fatigue

When insulin isn’t working properly, glucose remains in the bloodstream instead of entering the cells where it’s needed for energy. As a result, cells are essentially “starved,” leading to persistent fatigue.

Frequent urination can also cause dehydration, which further worsens feelings of exhaustion and weakness.

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Ten Lesser-Known or Unusual Signs of High Blood Sugar

10. Unexplained weight gain—or weight loss

While weight gain is common with type 2 diabetes, unexplained weight loss can also be an early warning sign. Even if you’re eating more than usual, your body may start breaking down muscle and fat for energy because it can’t use glucose efficiently. This may also lead to muscle weakness and balance issues.

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9. Irritability or depression

Rapid blood sugar fluctuations can influence mood. High sugar and refined carbohydrates may disrupt gut bacteria, which play a major role in serotonin production—a chemical essential for mood regulation.

Research has shown that post-meal blood sugar swings are associated with anxiety, depressive symptoms, and difficulty concentrating in people with type 2 diabetes.

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8. Tingling or numbness in hands and feet

Nerve damage can begin long before diabetes is diagnosed. Elevated blood sugar damages small blood vessels that nourish peripheral nerves, leading to numbness, tingling, or a “pins and needles” sensation.

If untreated, this damage can progress to loss of sensation, increasing the risk of injuries, infections, and slow healing.

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7. Slow-healing wounds

High blood sugar impairs circulation and nerve function, especially in the legs and feet. Even small cuts or blisters may heal slowly and become infected. In severe cases, untreated wounds can lead to serious complications.

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6. Frequent yeast or urinary tract infections

Excess glucose creates an ideal environment for yeast and bacteria to grow. Recurrent yeast infections or UTIs may be a sign that blood sugar levels are consistently too high and immune defenses are compromised.

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5. Blurry vision

High blood sugar can temporarily change the shape of the eye’s lens, making it harder to focus. Vision may worsen after high-carb meals and improve once blood sugar stabilizes. If untreated, long-term damage to the eyes can occur.

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4. Bleeding or swollen gums

Diabetes increases the risk of gum disease, and gum infections can further raise blood sugar levels. Symptoms may include redness, inflammation, gum recession, pus, or even tooth loss if left untreated.

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3. Skin changes

Skin tags, darkened patches of skin (acanthosis nigricans), dryness, itching, painless blisters, and thickened skin can all be linked to insulin resistance and poor blood sugar control.

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2. Hearing loss

People with diabetes are nearly twice as likely to experience hearing loss. High or low blood sugar can damage the nerves and blood vessels of the inner ear, interfering with sound transmission.

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1. Fruity-smelling breath

A fruity odor on the breath may indicate diabetic ketoacidosis (DKA), a serious condition that occurs when the body breaks down fat instead of glucose for energy. This process releases ketones, which can become dangerous if they build up in the blood.

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When to See a Doctor

Many of these symptoms can be caused by other conditions, so experiencing one occasionally isn’t necessarily cause for alarm. However, persistent symptoms—especially multiple signs at once—should prompt medical testing.

Doctors typically check HbA1C, fasting glucose, and ideally insulin levels, since insulin resistance often appears years before blood sugar rises.

Reversing type 2 diabetes and prediabetes depends heavily on dietary and lifestyle changes. A nutrient-rich diet, regular physical activity, and targeted supplementation may help slow or even stop disease progression.

If you’ve been diagnosed with prediabetes or type 2 diabetes, addressing the issue early can make a meaningful difference in your long-term health.