What Does a High Glucose Level Mean?

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When it’s time for your annual checkup, your doctor may order routine blood tests to check basic health indicators. One of these tests might measure the amount of sugar in your blood — also known as a blood glucose test. Glucose is the main type of sugar the body uses as fuel. It powers everything from your muscles to your heart to your brain. But what does it mean when your blood sugar level is higher than normal?

A high blood glucose reading could mean several things, depending on the number and the circumstances at the time of the test. In most cases, your doctor will investigate with additional tests to determine the underlying cause and what treatment is necessary. Here’s what you need to know about your blood glucose results, the different types of blood glucose tests, and why they are important. 

What Does Glucose Do for the Body?

Glucose is your body’s primary source of fuel to all your cells and organs to keep them functioning at full capacity. Without it, your cells and organs wouldn’t have the energy they need to operate. Most of the glucose in the human body comes from the foods we eat. After we eat, food is digested and the carbohydrates (also known as carbs) get broken down to glucose. The glucose is moved into the blood to be used as fuel.

As glucose builds up in your blood after eating, the body secretes insulin. Insulin is a hormone that signals to the rest of your body to use the glucose or store it for later. This process keeps your blood sugar level within a normal range.

If your body does not produce or respond to insulin effectively, your blood glucose level can stay elevated. Persistently high blood sugar levels can cause damage to your body and lead to health problems such as diabetes. 

What Do High Blood Glucose Results Mean?

The most common reason why blood sugar climbs too high is a condition called diabetes (or prediabetes). Diabetes is a serious condition that affects 1 in 10 Americans, and prediabetes affects 1 in 3 Americans. When you have diabetes, your body is either not producing enough insulin (typically Type 1 diabetes) or not responding to insulin appropriately (typically Type 2 diabetes), causing glucose to build up in the blood. Prediabetes is a less severe form of diabetes that often leads to Type 2 diabetes if left untreated. The diagnosis of diabetes and prediabetes are often made by measuring the level of glucose in your blood.

Interpretation of your blood glucose results depends on when you completed blood work and what type of test was ordered by your doctor. The types of blood glucose tests and the numbers that might indicate diabetes and prediabetes are as follows:

  • Finger stick glucose test: After a finger prick, blood is placed on small paper strip and blood sugar is measured on a handheld device
    • Glucose ≥200 mg/dL may indicate diabetes
  • Routine/random blood glucose test: Blood sample taken at any time, regardless of the last time you ate
    • Glucose ≥200 mg/dL may indicate diabetes
  • Fasting blood glucose test: Blood sample taken when you haven’t eaten for 8-12 hours, since your blood glucose levels are higher after you’ve eaten
    • Glucose ≥126 mg/dL may indicate diabetes
    • Glucose between 100-126 mg/dL may indicate prediabetes
    • Glucose <100 mg/dL is normal
  • Oral glucose tolerance test: Measures your blood sugar level after not eating for 8-12 hours, drinking a sweetened liquid, and then waiting a period (1-3 hours) for your body to absorb the sugar before a blood sample is taken
    • Interpretation varies depending on amount of sugar and wait period
  • Hemoglobin A1c (HbA1c) test: Blood test that shows your average blood sugar level over the last 2-3 months
    • HbA1c ≥6.5% may indicate diabetes
    • HbA1c between 5.7-6.4% may indicate prediabetes
    • HbA1c <5.7% is normal

If a finger stick glucose or routine glucose test results are high, your doctor may order the other tests for confirmation.

Why Is High Blood Sugar a Bad Thing?

While glucose is a fuel for the cells that make up your organs, at high levels it can be toxic, causing internal damage over time. If blood sugar remains elevated for long periods without treatment, it can lead to several problems, including a higher risk of:

  • Type 2 diabetes
  • Poor circulation to your arms and legs which could ultimately lead to amputation of affected limbs
  • Loss of vision or blindness
  • Kidney disease
  • Heart attack
  • Stroke

While these conditions that can result from high blood sugar may sound scary, the good news is that prediabetes and diabetes are both treatable conditions. Early and consistent treatment can help reduce your blood sugar and may prevent these serious complications of diabetes.

What Does High Blood Sugar Feel Like?

When your blood sugar is high, you may not feel any immediate symptoms. But there are a few subtle changes you might notice that can indicate diabetes:

  • Excessive thirst or hunger
  • More frequent urination (especially at night)
  • Unintended weight loss
  • Tingling or numbness of the hands or feet
  • Dry skin

If your blood sugar rises to extremely high levels, however, there are some symptoms you might notice:

  • Headache
  • Confusion
  • Difficulty concentrating
  • Weakness
  • Fruity-smelling breath
  • Abdominal pain
  • Fatigue
  • Dry mouth

If you have symptoms of high blood sugar, you should contact your doctor or seek medical attention as soon as possible. Extremely high blood sugar levels can require urgent treatment.

How Can You Lower High Blood Sugar?

There are several ways to lower blood sugar, including making changes to your diet, exercising, and taking oral medications or injected medications. The best way for you to lower your blood sugar will depend on how high your blood sugar is, how long it has been elevated, and what type of diabetes you most likely have. 

  • Diet – In cases of prediabetes or early Type 2 diabetes, making lifestyle changes to your diet and exercise regimens can be effective in stopping or reversing the conditions. The CDC recommends eating a diet consisting of less than 200-225 grams of carbohydrates a day. Eating foods with a low glycemic index (like fruit, porridge, lentils and pasta) will help your body manage the carbohydrates at a slower pace and avoid spikes in your blood glucose level. 
  • Exercise – Exercise is also important both to lower blood sugar levels and reduce the risk of heart disease and stroke. Experts recommend 30 minutes per day of aerobic exercise (swimming, running, vigorous walking). Sedentary activities such as watching television should also be interrupted every 20-30 minutes with light activity.
  • Medications – In cases of more severe Type 2 diabetes or if lifestyle changes are ineffective, medication may be necessary to help lower your blood sugar. There are many different medications that help lower blood sugar. Your doctor will decide which ones will be best for you based on your other health conditions and medications. In some cases, insulin injections may be necessary to reverse high blood glucose when your pancreas is not producing enough. This is usually necessary in Type 1 diabetes, and sometimes necessary in severe Type 2 diabetes. 

Some individuals with diabetes, especially those on insulin, may need to monitor their own blood glucose levels daily — or even several times a day. You can either use a finger prick method or a continuous glucose monitor (CGM). Your doctor can help you decide whether it is necessary to check your blood glucose and help you find a monitor that’s right for you.

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