How to test your blood sugar levels and why it's critical for some people

When it comes to maintaining health, it can be helpful to understand an optimal baseline for some matters. Learning a healthy weight range for your height, age, and gender, for instance, can be useful in determining body composition needs. It can also be helpful to understand things like blood pressure readings, what a healthy resting heart rate is, and what high and low cholesterol levels are.

Another barometer of health that some want to be aware of is their blood sugar levels. While the body does a good job of regulating blood sugar levels in people without diabetes, some healthy people still choose to check or monitor these levels from time to time.

What is blood sugar?

Blood sugar, also called blood glucose, is simply the sugar in your bloodstream that comes from the food your body has broken down during digestion. With the help of insulin and other hormones, it becomes absorbed by your cells and organs to fuel your body and mind with energy.

While blood sugar is essential to survive, when blood sugar levels get too high, one may have a condition called hyperglycemia that may cause brain fog, frequent urination, blurred vision, frequent hunger pangs, and one's wounds to heal slowly. Chronic high blood sugar levels can also be indicative of diabetes and other medical conditions. "Serious issues arise from sustained overload of sugar in your bloodstream for very long periods of time," says Kristina Cooke, a registered dietitian who specializes in diabetes treatment and prevention.

On the opposite side, when blood sugar levels are too low, called hypoglycemia, one may experience symptoms such as shakiness, headache, nausea, irritability and fatigue.

Monitoring or managing one's blood sugar levels can be helpful for anyone, but doing so is critical for people with diabetes. "Learning the tools for how to keep blood sugars within normal range with nutrition, exercise, other lifestyle factors and sometimes medication is key for someone living with diabetes," says Cooke.

What is normal blood sugar?

People with diabetes should aim to keep their blood sugar levels between 70 and 180 milligrams (mg) per deciliter (dL), says Dr. Sun Kim, an endocrinologist at Stanford University who specializes in treating diabetes. Otherwise, "we know that chronically high blood sugars can damage blood vessels and nerves," she explains. Because of such complications, "diabetes is the number one cause of blindness, kidney failure and need for amputations," she adds.

People without diabetes generally have no issues naturally keeping their blood sugar levels in a normal range, which is anything between 80 to 130 mg/dL before eating, or under 180 mg/dL for the first couple of hours after eating. "All healthy people will see a rise in blood sugar numbers after consuming food when glucose first hits the bloodstream and before it's absorbed," says Cooke.

How to test your blood sugar levels

There are several ways of testing your blood sugar levels, both in clinical settings and at home, though various measurements and standards are used to determine healthy or concerning results throughout each method.

When one is having blood sugar levels tested to check for type 2 diabetes or prediabetes at a doctor's office, for instance, a trained physician will oversee and interpret one of the following tests, per the U.S. Centers for Disease Control and Prevention:

  • A1C tests measure one's average blood sugar level over multiple months.

  • Fasting blood sugar tests specifically measure one's blood sugar levels in the morning to ascertain a fasting blood sugar level. Using this test, a fasting blood sugar level of 99 mg/dL or lower is considered normal, while 100 to 125 mg/dL indicates you have prediabetes, and 126 mg/dL or higher indicates you have diabetes.

  • Glucose tolerance tests measure one's blood sugar before and after drinking a specialized liquid that contains glucose. This test usually requires measuring one's blood sugar levels at different 1-, 2-, and 3-hour intervals after drinking the liquid.

  • Random blood sugar tests don't require any fasting or advanced preparation. Using this test, a blood sugar level reading of 200 mg/dL or higher indicates you have diabetes.

When testing one's blood sugar levels at home, some use a blood sugar meter to prick their finger so that a drop of blood can be tested by the medical device.

Continuous Glucose Monitors (CGM) are another option both for people with diabetes and without. When using a CGM, one wears a small attachment that constantly estimates and reports what their blood sugar levels are throughout the day.

Though once only used by people with diabetes, CGM's are growing in popularity as other individuals are also paying attention to the way various foods impact their blood sugar levels and the way those foods make them feel.

While Kim says that such information can be helpful to have and that there's nothing wrong with anyone interested wearing a CGM for a week or two, she says most people can save the money and time and keep their blood sugar levels in a healthy range through healthy diet and exercise. "You would spend your money and time more wisely by exercising regularly and eating less processed foods and added sugars and eating more vegetables and fruits," she says.

More: Glucose, insulin and why levels are important to manage. Here's why.

This article originally appeared on USA TODAY: What is normal blood sugar? Plus how to test your levels