Understanding how blood sugar and diabetes are related

The amount of sugar (also known as glucose) in the blood, or blood sugar level, can impact one’s health status. The body uses sugar or glucose in the blood as an energy source. If blood sugar is too high (high blood sugar), it could be the first sign of diabetes and can cause damage to organs if left untreated. If someone has low blood sugar, it can affect how well they function and, in severe cases, cause organ damage, loss of consciousness, coma or even death. 

Keeping blood glucose levels in a healthy range can help prevent (or delay) diabetes, heart disease, obesity, and other health problems. Keep reading to learn more about how blood sugar levels and diabetes are related.

In this article:

What is blood sugar?

Much of the food a person eats is converted into simple sugars (such as glucose) that is then released into the bloodstream. Blood sugar starts to rise within 30 minutes after a person has eaten (although this can vary depending on different foods and other factors). 

“Different factors impact how much your blood sugar increases after eating,” according to Jennie Stanford, MD, dual board certified in family medicine and obesity medicine. “Different foods affect blood sugar differently, as well as the other nutrients within the meal. Certain health conditions (like insulin resistance) and specific medications (like steroids and antipsychotics) can have varying effects on blood sugar too,” she adds.

The body can also make blood sugar from stored glucose in the liver and other substances like amino acids. The kidneys can also make small amounts of blood sugar.

The body keeps blood sugar levels in check primarily through insulin, a hormone that the cells (called beta cells) in the pancreas make. When blood sugar rises, these beta cells release insulin, allowing the sugar in the blood to enter the body’s cells, where it can be used for energy. 

Importance of blood sugar in the body

Blood sugar provides the brain and body with energy. Although every organ needs glucose to function, the brain relies on it the most for fuel, using about 60 percent of the body's blood glucose while at rest.

Carbohydrates are the body’s main source of glucose because they are metabolized into glucose in the body—but not all carbohydrates are created equal. Complex carbohydrates have the most health benefits because they contain fiber, minerals and vitamins. They include beans, fruits, vegetables, whole grains and other fiber-rich foods. The recommended amount of carbohydrates differs based on individual factors.

How blood sugar is measured

Blood sugar levels are measurements that indicate the amount of sugar in the blood. There are different methods for testing blood sugar levels. A health care provider will determine the appropriate tests.

Testing methods

There are numerous ways to test blood sugar levels, including various blood tests and at-home monitors. These testing methods include the following:

• Blood glucose meter. This involves testing the sugar levels in a finger-prick blood sample using a device called a blood glucose monitor or meter. It is the most common way to measure blood sugar. A person can take this test at home and generally does not require assistance from another person to administer. 
• Continuous glucose monitor. A continuous glucose monitor is a wearable device that checks and records blood sugar levels round-the-clock.
• Fasting blood sugar test. This test checks blood sugar levels only after a person has fasted or has not taken food or drink (except water) overnight (or having fasted for at least eight hours before the test). 
• Glucose tolerance test. This test looks at the body’s ability to metabolize sugar (glucose). It involves checking blood glucose at one or two hours after drinking 75g of sugar.
• Random blood sugar test. This test checks blood sugar levels at any time of the day.
• The HbA1C test. This test checks average blood sugar levels over the past two or three months. A person can take this test whether or not they’re fasting.

Normal blood sugar levels

A normal blood sugar level is when blood sugar is measured and is within a healthy range, neither too high nor too low. 

Fasting blood sugar

Fasting blood sugar is the sugar in the blood when a person hasn’t eaten or had any drinks (except water) for eight to 12 hours. Blood sugar levels are measured in millimoles per liter (mmol/L) or milligrams per deciliter (mg/dL). Normal fasting blood sugar levels range between 70 and 100 mg/dL (3.9 and 5.6 mmol/L).

Blood sugar levels

If a person isn’t pregnant and has diabetes, it is recommended that their blood sugar levels stay within these targets:

• A1C: Less than 7% or 154 mg/dL
• Before a meal: 80–130 mg/dL
• An hour or two after starting a meal: Less than 180 mg/dL

However, it is important to know that many patients may have different blood sugar targets based on individual factors. For many people, an HbA1c goal of < 7% is best, while others need a target of 8%.

A health care provider can best recommend blood sugar targets for each case after considering factors, including the following:

• Age
• How long a person has had diabetes
• Other health conditions or diabetes complications
• Specific health needs and other concerns

Factors affecting blood sugar levels

Blood sugar levels usually remain within a normal range in people without diabetes, neither dropping too low nor rising too high. However, in people with diabetes, sugar levels can fluctuate depending on a few factors.

Food and diet

Blood sugar levels can rise or drop depending on what someone eats, how much and when. For example, consuming too many carbs can cause blood sugar levels to rise too high. On the flip side, having too few carbs or missing a meal can cause a dangerous drop in blood sugar levels. Drinking alcohol on an empty stomach can cause blood glucose to drop to a much lower level.

Physical activity

Exercise can help the body respond better to insulin and keep blood sugar levels in a healthy range. Prolonged inactivity can cause blood sugar levels to rise, and too much activity without proper nutrition can cause blood sugar levels to drop.

Stress and hormonal changes

Stress and hormonal changes can also affect blood sugar levels. Factors like illness, pain, work-related stressors and hormonal changes when a person is menstruating or pregnant can make the body send out hormones that cause blood sugar levels to rise.

Sleep

Sleep can also affect blood sugar and insulin levels. Without adequate sleep, higher-than-normal blood sugar and insulin levels can develop, increasing the risk of insulin resistance.

Medications

Not following the correct dose when taking diabetes medication can raise blood sugar levels or make them drop to lower-than-usual levels. 

Some medications, such as those used to treat irregular heartbeats and infections, can also cause a drop in blood sugar levels. Other medications, like steroids and antipsychotics, may cause elevated blood sugar levels.

High blood sugar (hyperglycemia)

High blood sugar, or hyperglycemia, is a condition that happens when a person has too much sugar in their blood. High blood sugar often occurs in people with prediabetes and diabetes. Left untreated, it can lead to organ damage and serious health problems.

 A blood glucose reading over 140 mg/dL is considered high anytime for those without diabetes.

Causes of high blood sugar

When the body doesn't make enough insulin to regulate blood sugar or use insulin properly (a condition called insulin resistance), it leads to high blood sugar. In this case, that sugar stays in the blood, and the cells can't use it for energy.

High blood sugar can also happen when a person has health problems involving organs like the pancreas and adrenal glands, or hormonal issues or conditions like Cushing’s syndrome. High blood sugar can also happen as a side effect of some medicines like antipsychotics, antiseizure and steroid medications.

Symptoms and complications of hyperglycemia

People with high blood sugar may have the following symptoms:

• Increased thirst
• Frequent urination
• Feeling weak or tired
• Blurred vision

Left untreated or poorly managed, hyperglycemia can cause serious health problems. Complications of hyperglycemia include eye disease, gum disease, heart disease, kidney disease and nerve damage.

Management and treatment of hyperglycemia

If someone has high blood glucose levels, they should see a health care provider whether or not they have diabetes. A health care provider may recommend a treatment plan that includes dietary changes and increased physical activity.

Low blood sugar (Hypoglycemia)

Hypoglycemia, or low blood sugar, happens when a person’s blood sugar levels drop to a lower-than-normal value. A blood glucose reading lower than 70 mg/dL is considered low in people with diabetes. The potential impacts of different levels of hypoglycemia vary.

Causes

Low blood sugar can happen as a side effect of diabetes medications like insulin and diabetes pills. Other factors that can cause low blood sugar include not eating enough carbohydrates, missing meals, consuming nutritionally imbalanced meals, being too physically active, or drinking alcohol.

Symptoms and complications of hypoglycemia

Symptoms of hypoglycemia can happen suddenly and show up in different ways in different people. They include:

• Confusion
• Dizziness
• Fast heart rate
• Feeling hungry
• Headache
• Irritability
• Shakiness
• Tiredness 

Hypoglycemia can also cause a person to lose consciousness, which can have serious consequences, especially when it happens at work or while driving.

Management and treatment of hypoglycemia

Consuming 15 to 20 grams of glucose — or foods or drinks with carbohydrates and sugars, like apple juice, grape juice, hard candy, honey or soda — can quickly return low blood sugar levels to normal. If a person has diabetes, they should check their blood sugar levels before having foods or beverages with carbohydrates. Once they’ve consumed the carbs, they should check again to see if their blood sugar has returned to normal.

Blood sugar and diabetes

Diabetes is a chronic condition that happens when blood sugar stays too high. A person with diabetes usually has higher-than-normal blood sugar levels because the body makes little or no insulin, or doesn’t use the available insulin properly, causing sugar to remain in the blood rather than enter cells for energy. There are three main types of diabetes: type 1, type 2 and gestational.

Type 1 diabetes

Type 1 diabetes is an autoimmune condition that occurs when the immune system attacks and damages beta cells in the pancreas, causing the body not to produce sufficient insulin (or to produce none at all).

People with type 1 diabetes often have symptoms like blurred vision, hunger, excessive urination, increased thirst, tiredness and unexplained weight loss. Type 1 diabetes can develop in anyone at any age. While no one knows exactly why it happens, genetics and environmental triggers can be contributing factors. Type 1 diabetes cannot be prevented, and treatment typically involves lifelong insulin therapy.

Type 2 diabetes

Type 2 diabetes occurs when the body’s cells don’t respond well to insulin. When cells don’t use insulin properly, the body makes more insulin to regulate blood glucose levels and get sugar to enter cells. Over time, the body won’t be able to produce enough insulin, and blood sugar levels will remain high.

Type 2 diabetes can happen to anyone, too, but it is more common in adults. People with type 2 diabetes may not have any noticeable symptoms for a period of time but may later start showing symptoms like blurred vision, excessive urination, hunger, increased thirst, slow-healing wounds, tiredness or weight change.

Type 2 diabetes develops over time due to different factors, including having overweight or obesity, being sedentary, having insulin resistance, or having genes that predispose a person to diabetes.

Lifestyle choices may help prevent the onset of type 2 diabetes. These include adopting healthy lifestyle habits like exercising and eating nutrient-dense foods like fruits, healthy fats, lean proteins, vegetables and whole grains.

A health care provider may recommend taking diabetes medications and making healthy lifestyle changes.

Gestational diabetes

Gestational diabetes only occurs in pregnant people and is often diagnosed in the 24th to 28th week of pregnancy. People with this condition may not have any symptoms, but when they do, symptoms may include frequent thirst and urination. 

Gestational diabetes may happen due to hormonal changes in pregnancy that cause the body not to be able to make enough insulin or use insulin as well as it used to. Having overweight or having genes that predispose a person to diabetes may also cause gestational diabetes.

A health care provider may recommend exercise and a healthy eating plan to manage gestational diabetes. In some cases, they may recommend insulin to help keep blood sugar levels in a safe range. Having gestational diabetes may increase a person’s risk of developing type 2 diabetes after delivery and later in life.

Monitoring blood sugar in diabetes management

Monitoring blood sugar levels is crucial for effective diabetes management and treatment. It helps health care providers and people with diabetes learn how well treatment is working and decide whether any changes need to be made to the treatment plan. 

Managing blood sugar levels can also help prevent or delay the onset of severe health complications of diabetes, including heart disease, kidney issues and vision problems. Monitoring blood sugar levels is a significant part of staying healthy with diabetes in the long run.

If a person suspects that someone’s blood sugar levels may be high or they experience symptoms that suggest high blood sugar, they should consult a health care provider. They can perform necessary tests and recommend treatment if needed.

Frequently asked questions

What is a normal blood sugar range?

Normal fasting blood sugar ranges between 70 mg/dL (3.9 mmol/L) and 100 mg/dL (5.6 mmol/L) and normal blood sugar during other times may range from 70-140 mg/dl.

What is the difference between blood sugar and diabetes? 

Blood sugar is the sugar in the blood, while diabetes means a person has high blood sugar levels outside of the normal range.

This content is for informational purposes only and is not medical advice. Consult your health care provider before taking any vitamins or supplements and prior to beginning or changing any health care practices.