Diabetes: Symptoms, causes, treatment

Woman checking blood sugar level while sitting on bench. Maskot via Getty Images — Woman checking blood sugar level while sitting on bench.

(Image credit: Maskot via Getty Images)

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Types of diabetes
Prevention & risk factors
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Diabetes is a chronic disease characterized by high blood sugar, or glucose.

This glucose, which is derived from the food we eat, is a critical source of energy for the body's cells. Once glucose enters the blood, the pancreas releases the hormone insulin, which shepherds the glucose from the blood into cells, feeding them their essential fuel.

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About 11.3% of the U.S. population, or 37.3 million people, has diabetes, according to a recent report from the Centers for Disease Control and Prevention (CDC); about 8.5 million, or 23%, of those people have undiagnosed diabetes. In addition, about 96 million people in the U.S. have prediabetes, a condition in which blood sugar levels are high but not high enough to be diagnosed as diabetes, but most are unaware of it.

Gestational diabetes happens when someone who did not previously have diabetes develops diabetes during pregnancy. During pregnancy, the hormones produced to sustain the pregnancy, such as estrogen and cortisol, make the pregnant person's own cells more resistant to insulin, according to Johns Hopkins Medicine. Normally, the pancreas produces more insulin to compensate, but sometimes, it can't keep up, allowing glucose to build up in the bloodstream. Sometimes, gestational diabetes resolves after pregnancy; other times, the condition becomes chronic.

Genetics plays a role in type 2 diabetes, so someone who has a family history of the disease is more likely than others to develop it, according to the National Institutes of Health. Other factors that increase a person's chances of developing this type of diabetes include: being 45 years or older, being overweight or obese, having other health conditions such as high blood pressure, along with other risk factors, the NIH says. A person who is African American, American Indian, Asian American, Pacific Islander or Hispanic American, has an increased risk of developing type 2 diabetes, according to the CDC.

Diabetes dramatically raises the likelihood of heart disease and other cardiovascular events, including heart attacks and strokes, according to a review of existing research published in 2015 in the World Journal of Diabetes. It all stems back to persistent high sugar levels, which over time can damage the arteries that carry blood, oxygen and nutrients around the body, says the British Heart Foundation. Once the arteries are damaged, it’s easier for fat to clog up arterial walls and limit blood flow. If the arteries carrying blood to the heart are obstructed, it can lead to a heart attack — if the arteries carrying blood to the brain get congested, that can culminate in stroke.

Nerve damage is also a common complication , as excess sugar can impair the walls of the tiny blood vessels that nourish the nerves, eventually leading to a condition called neuropathy, or a loss of all sense of feeling in the affected limbs that affects more than 90% of people living with diabetes, according to a 2015 study published in the World Journal of Diabetes. That nerve trauma may also make people more vulnerable to infections and lead sores and cuts to heal more slowly. In particular, people with diabetes are susceptible to problems in their legs and feet, which can result in amputation if left untreated, says the Mayo Clinic.

Diabetes can also damage the kidneys, which contain millions of blood vessel clusters that filter waste in blood. If left unaddressed, a person with kidney damage resulting from diabetes may need dialysis, or even a kidney transplant. Research suggests that diabetes has become the single most frequent cause of end-stage kidney disease, according to a 2019 paper published in the journal Molecular Metabolism. Uncontrolled blood sugar can also weaken the blood vessels of the eye (diabetic retinopathy) to the point of causing blindness, says the Mayo Clinic.

A common but severe complication of type 1 diabetes (and, less commonly, type 2 diabetes) is diabetic ketoacidosis, which occurs when there is a drastically low level of insulin in the body, according to the National Library of Medicine. This means the body can't use sugar for energy, so it starts to use fat instead. As a result, compounds called ketones are released, causing the blood to become acidic and, in turn, toxic. Diabetic ketoacidosis is sometimes the first sign of type 1 diabetes in people who haven't been diagnosed; if left untreated, it can be deadly.

The American Diabetes Association recommends screening for type 2 diabetes for all adults age 45 and older, as well as for: Individuals who are overweight or have obesity, plus have one or more diabetes risk factors; women who have had gestational diabetes; people with prediabetes; kids who are overweight or have obesity, and have a family history of type 2 diabetes or one or more other risk factors, according to the Mayo Clinic.

Normal blood sugar levels vary from person to person, but a normal range for fasting blood sugar (the amount of glucose in your blood at least eight hours after a meal) is between 70 and 100 milligrams per deciliter (mg/DL), according to the World Health Organization (WHO). According to the ADA, the normal blood sugar range two hours after someone eats is generally less than 140 mg/DL, according to the ADA.

One method is the A1C blood test, which measures average blood glucose over the preceding three months. The test measures glucose attached to hemoglobin, the oxygen-carrying protein in blood. The red blood cells that carry this protein live for about three months, so measuring them at a single time point provides a snapshot of the general level of glucose in the blood. An A1C result of less than 5.7% is considered normal, between 5.7% and 6.4% suggests prediabetes, and 6.5% or greater indicates diabetes.
Another test, the fasting plasma glucose test, reveals how effectively the body metabolizes glucose and requires the patient to fast for eight hours before taking the test. More than 126 mg/DL of glucose in the blood signals diabetes.
The oral glucose tolerance test, which is often used to detect gestational diabetes, requires the patient to consume a very sugary drink. Two hours later, the person undergoes a blood test. A repeated result of 200 mg/DL or greater of glucose in the blood would mean a diabetes diagnosis.
Given that a family history of diabetes raises the risk of developing the condition, people who fall into that category should talk to their doctor about being screened.

People with diabetes are usually asked to regularly monitor their blood sugar levels in order to keep an eye on the impact of medication, diet and exercise on their glucose levels, says the Mayo Clinic. Keeping track of these levels can be done by either using a device called a continuous glucose monitor (CGM), which measures blood sugar every few minutes using a sensor inserted under the skin, or with the help of a portable electronic device called a blood sugar meter using a small drop of blood.

In 2016, the FDA approved the use of an "artificial pancreas" that automatically tests blood glucose levels periodically and releases insulin accordingly, Live Science previously reported. The product relies on a coin-size transmitter attached to a tiny needle that is inserted into the skin to continuously track glucose levels, a pump that delivers precise doses of insulin as needed through a separate catheter, and a computer chip that uses data from both components to optimize the delivery of insulin on a minute-by-minute basis.

There is no cure for type 2 diabetes either, but with substantial and sustained weight loss, patients can go into remission, which means their blood sugar levels fall into the normal range again, according to the NIH. However, this doesn't mean the person has been "cured" or completely rid of diabetes for good, because blood glucose levels tend to fluctuate with weight, so if the person regains the weight, their blood sugar levels could elevate to a diabetic range back again.

Bahar Gholipour is a staff reporter for Live Science covering neuroscience, odd medical cases and all things health. She holds a Master of Science degree in neuroscience from the École Normale Supérieure (ENS) in Paris, and has done graduate-level work in science journalism at the State University of New York at Stony Brook. She has worked as a research assistant at the Laboratoire de Neurosciences Cognitives at ENS.

With contributions from

Stephanie PappasLive Science Contributor

Diabetes: Symptoms, causes and treatment

Types of diabetes

Prevention & risk factors

Symptoms & complications

Diagnosis

Treatment

Is diabetes curable?

Additional resources

Bibliography