Glucose Levels: Why It's Important to Monitor

Blood sugar level is the amount of glucose in the blood. Glucose is the main sugar found in the bloodstream, and its level can rise and fall for various reasons and throughout the day. It comes from the food you eat, and is your body's main source of energy.

Our bodies digest the food we eat in the stomach, where the carbohydrates in the food break down into glucose. The stomach and small intestines then absorb the glucose and release it into the bloodstream. Once in the bloodstream, glucose can be used immediately for energy or stored in our bodies to be used later. Insulin helps our bodies use or store glucose for energy. When your body doesn't make enough of this essential hormone or can't use it well, like in the case of diabetes, glucose stays in the bloodstream and keeps blood sugar levels high.

Regular blood sugar monitoring is recommended for people with type 1 or type 2 diabetes. Knowing what affects your blood sugar level can help your healthcare team make decisions about your best diabetes care plan. This can help delay or prevent diabetes complications, such as heart attack, stroke, kidney disease, vision loss, and amputation.

Woman at a table taking her blood sugar level with a pen

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Glucose Levels: What You Need to Know

Glucose levels will naturally rise and fall throughout the day. For example, after a meal they will rise, and you may experience a fall in glucose levels after an exercise.

Blood glucose can be low, normal, or high. A normal glucose level will be different based on how long someone has had diabetes, age, and other health conditions. However, the American Diabetes Association has standard blood glucose recommendations for people living with diabetes:

  • Before meals: 80 to 130 mg/dL
  • One to two hours after meals: Less than 180 mg/dL

Hypoglycemia, or low blood sugar, is defined as a glucose level of less than 70 mg/dL or slightly higher, while hyperglycemia, high blood sugar, is characterized as a glucose level of greater than 125 mg/dL while fasting (not eating for at least eight hours). A person with a fasting blood glucose of higher than 125 mg/dL is said to have diabetes, and someone who has prediabetes will have a fasting blood glucose of 100 mg/dL to 125 mg/dL.

Who Is Most at Risk?

While blood sugar level fluctuates in everyone, some people are at higher risk for hyperglycemia or hypoglycemia than others.

For hyperglycemia, the risk is higher for those who:

  • Have type 2 diabetes in the family
  • Are African American, Native American, Hispanic, or Asian American
  • Are overweight
  • Have high blood pressure or cholesterol
  • Have polycystic ovarian syndrome
  • Have a history of gestational diabetes (diabetes during pregnancy)

On the other hand, hypoglycemia is most common in people with diabetes and very rarely occurs in those who don't have the condition. It can develop if food, exercise, and diabetes medications are out of balance.

Common pitfalls for people with diabetes include:

  • Being more active than usual
  • Drinking alcohol without eating
  • Eating late or skipping meals
  • Not balancing meals by including fat, protein, and fiber
  • Not eating enough carbohydrates
  • Not timing insulin and carb intake correctly (for example, waiting too long to eat a meal after taking insulin for the meal)

If someone with diabetes uses the wrong insulin, takes too much of it, or injects it incorrectly, that can also lead to hypoglycemia.

Who Is More at Risk of Diabetes?

People who have a family history of type 1 diabetes are more likely to develop this form of the disease. It is also more common in children, adolescents, and young adults. Risk factors for type 1 diabetes are not as clear as those for type 2 diabetes.

A person is more at risk of developing type 2 diabetes if they:

  • Have prediabetes
  • Are overweight
  • Are 45 years or older
  • Have a family history with type 2 diabetes
  • Are physically active less than three times a week
  • Have a history of gestational diabetes or have given birth to a baby weighing more than 9 pounds
  • Are African American, Hispanic or Latino American, American Indian, or Alaska Native (some Pacific Islanders and Asian Americans are also at higher risk)
  • Have a history of nonalcoholic fatty liver disease

Glucose Levels: Fluctuation Causes

A number of factors can cause a person's blood sugar to go up or down.


Some medications can severely raise, or less often, lower blood glucose levels. Medications that can lead to these fluctuations include:

These medications affect blood sugar levels because they can cause insulin to become more or less sensitive. Diabetes medications can also cause fluctuations in blood glucose levels if you are not taking enough or too much of the medications or if the amount of carbohydrates you are eating or drinking is not balanced with the amount of insulin you inject.

It's vital to discuss any symptoms or concerns with your healthcare provider and keep your medical team in the loop about the medications you're taking and any changes to the dosage.

Other Factors

Other factors that can contribute to high blood glucose include:

  • Too much food, such as a meal or snack with more carbohydrates than usual
  • Not being active
  • Not enough insulin or oral diabetes medications
  • Illness (your body releases hormones to fight the illness, and those hormones raise blood glucose levels)
  • Stress
  • Short- or long-term pain, such as pain from a sunburn
  • Menstrual periods
  • Dehydration

Factors that can lead to low blood sugar include:

  • Not enough food, such as a meal or snack with fewer carbohydrates than usual or a missed meal or snack
  • Alcohol, especially on an empty stomach
  • Too much insulin or oral diabetes medications
  • More physical activity or exercise than usual (physical activity makes your body more sensitive to insulin and can lower blood glucose)

Why Is It Important to Monitor Glucose Closely?

Monitoring blood glucose closely allows you to identify what is causing your levels to fluctuate so you can avoid things that are affecting you. Keeping a close eye on this number also allows you to catch low or high blood sugar early and avoid hypoglycemia or hyperglycemia.

For people with diabetes, blood sugar numbers show how well their diabetes is managed and managing their diabetes means that they have a lower chance of having serious health problems, such as kidney disease and vision loss.

It's also important to log any changes in blood sugar level so they can be shared with healthcare providers who can use it to make the best care plan or any adjustments to existing treatments.

There are two ways to measure blood sugar:

  • Blood sugar checks that you do yourself with a glucometer
  • The A1C test done in a lab or at your provider’s office, which tells you your average blood sugar level over the past two to three months

Managing Glucose Levels

Eating a healthy diet with plenty of fruit and vegetables, maintaining a healthy weight, and getting regular physical activity can all help. Other tips for managing your glucose levels include:

  • Eat at regular times, and don’t skip meals
  • Choose foods lower in calories, saturated fat, trans fat, sugar, and salt
  • Track your food, drink, and physical activity
  • Drink water instead of juice or soda
  • Limit alcoholic drinks
  • For a sweet treat, choose fruit
  • Control your food portions

If you have concerns or are struggling living with diabetes, your healthcare team is a resource for information on natural treatments and medications. Be sure to discuss lifestyle and medication changes and ask questions to better manage and monitor your glucose levels daily.

A Word From Verywell

Monitoring blood sugar is the most important part of managing diabetes. While glucose is essential to the body, unmonitored fluctuations can lead to hyperglycemia or hypoglycemia. These dangerously high or low levels can lead to severe complications. While these symptoms and complications are scary, they are avoidable and working with your healthcare team is a big part of that. If you have concerns about blood sugar levels, work with your healthcare team to monitor and make changes to lifestyle or medications.

Frequently Asked Questions

  • How can you lower glucose levels?

    Lifestyle modifications such as getting regular exercise and following recommendations for diet can help with lowering glucose levels over time. Depending on the type and severity of the diabetes, insulin or other medications may also be needed. If your blood sugar is above 240 mg/dL, check with your doctor.

  • What are normal glucose levels?

    A fasting blood sugar level of 99 mg/dL or lower is considered normal. Your blood sugar is tested after an overnight fast, meaning you don't eat until after the test is taken.

  • How does insulin regulate blood sugar levels?

    Insulin is a hormone that allows glucose to move from your blood into your cells. It also signals the liver to store blood sugar for later. Glucose can build up in your blood if your cells don't respond to the insulin or your body doesn't make enough insulin.

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10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Manage blood sugar.

  2. American Diabetes Association. Hyperglycemia (high blood glucose).

  3. Cleveland Clinic. Hypoglycemia (low blood sugar).

  4. Centers for Disease Control and Prevention. Diabetes risk factors.

  5. Jain V, Patel RK, Kapadia Z, Galiveeti S, Banerji M, Hope L. Drugs and hyperglycemia: a practical guide. Maturitas. 2017 Oct;104:80-83. doi:10.1016/j.maturitas.2017.08.006

  6. Good to know: factors affecting blood glucose. Clin Diabetes. 2018 Apr;36(2):202. doi:10.2337/cd18-0012

  7. McDonnell M, Umpierrez G. Insulin therapy for the management of hyperglycemia in hospitalized patientsEndocrinol Metab Clin North Am. 2012;41(1):175-201. doi:10.1016/j.ecl.2012.01.001

  8. American Diabetes Association. Hyperglycemia (high blood glucose).

  9. Centers for Disease Control and Prevention. Diabetes tests.

  10. Centers for Disease Control and Prevention. Insulin resistance and diabetes.