What Causes Type 2 Diabetes?

• By Madeline R Vann, MPH
• Medically Reviewed by Christine Wilmsen Craig, MD

Eating too much and exercising too little can increase your risk for developing type 2 diabetes.

Insulin is a hormone made in the pancreas that allows glucose (sugar) to leave the bloodstream and enter the cells to be used as fuel.
Type 2 diabetes occurs when the pancreas doesn't make enough insulin, or the cells of the body become resistant to insulin.
It's not known for certain why some people develop type 2 diabetes and some do not. There are several factors, however, that can increase a person's risk of developing type 2 diabetes.

Primary Causes of Type 2 Diabetes

Being obese or overweight puts you at significant risk for developing type 2 diabetes. Four out of five people with type 2 diabetes are overweight or obese.
"One of the links with obesity is that fat induces a mild, low-grade inflammation throughout the body that contributes to heart disease and diabetes," says Vivian Fonseca, MD, professor of medicine and pharmacology and chief of endocrinology at Tulane University Health Sciences Center in New Orleans.
Excess fat, especially abdominal fat, also changes the way that your body responds to insulin, leading to a condition called insulin resistance. With this condition, your cells cannot use insulin to process blood sugar out of the blood, resulting in high blood sugar levels.
While not everyone with insulin resistance develops diabetes, people with insulin resistance are at increased risk of type 2 diabetes.

Poor Eating Habits

Eating too much of the wrong kinds of foods can increase your risk of type 2 diabetes. Studies have shown that eating a diet of calorie-dense, refined foods and beverages, such as sodas or fruit juices, and too little raw fruits, vegetables, and whole grains can significantly increase your risk of type 2 diabetes.

Too Much TV Time

An analysis of health and nutrition data from a nationally representative sample of adults between the ages of 20 and 54 years of age showed that people who watched television more than two hours a day were more likely than their peers to be obese and to have diabetes.
This is probably due to snacking while watching TV. The study found that the frequent TV watchers consumed, on average, 137 more calories a day than their peers. Conversely, the data indicated that cutting TV time back to less than 10 hours a week and adding a daily 30-minute walk led to 43 percent fewer cases of diabetes in the study group.

Physical Inactivity

Just as body fat interacts with insulin and other hormones to affect diabetes development, so does muscle. Lean muscle mass, which can be increased through exercise and strength training, plays a role in protecting the body against insulin resistance and type 2 diabetes.
A six-month study of 117 older men and women with abdominal obesity recently demonstrated that a mix of aerobic and resistance training exercises helped to reduce insulin resistance.

Sleep Habits

Sleep disturbances have been shown to affect the body’s balance of insulin and blood sugar by increasing the demand on the pancreas. Over time, this can lead to type 2 diabetes.
An analysis of data from 8,992 adults who participated in the First National Health and Nutrition Examination Survey showed that over the course of a decade, those who slept fewer than five hours a night or more than nine were at increased risk of type 2 diabetes.

Genetics

Genes play an important role in determining a person's risk of type 2 diabetes. Researchers have identified at least 10 genetic variations linked to increased risk for this disease. However, your genes are not your fate; diet and exercise can prevent type 2 diabetes even if you have family members with the condition.

What Is Hyperglycemia?

• By Ingrid Strauch
• Medically Reviewed by Sanjai Sinha, MD

Hyperglycemia is the medical term for high blood glucose, or high blood sugar.

Did you know that you have sugar in your bloodstream at all times? In fact, your blood sugar levels fluctuate over the course of the day.
Levels are higher right after meals (as carbohydrates are broken down into glucose and enter the bloodstream through the small intestine) and lower after exercise (when glucose has been burned to fuel the activity).
In someone who doesn't have diabetes, blood sugar levels stay within a narrow range. Between meals, the concentration of sugar in the blood ranges from about 60 to 100 mg/dl (milligrams per deciliter).
After meals it may reach 120 to 130 mg/dl, but rarely goes higher than 140 mg/dl.
But if you have type 2 diabetes, blood sugar levels can go much higher — to 200, 300, or even 400 mg/dl and beyond — and will go much higher unless you take the necessary steps to bring them down.

Diagnosing Type 2 Diabetes

All types of diabetes are diagnosed on the basis of hyperglycemia. Several different types of blood tests may be used to make the diagnosis, including:

• fasting plasma glucose test
• random glucose test
• HbA1c test
• oral glucose tolerance test

When screening for diabetes in a person with risk factors for type 2 diabetes, doctors generally order either a fasting plasma glucose test (which requires fasting for 8 to 10 hours) or an HbA1c test (which does not require fasting).
A fasting plasma glucose test result of 126 mg/dl or higher indicates diabetes, as does an HbA1c test result of 6.5 percent or higher.
A fasting plasma glucose test result between 100 and 125 mg/dl and an HbA1c test result between 5.7 percent and 6.4 percent indicate prediabetes, which is associated with a high risk of developing type 2 diabetes in the future.
A random glucose test may be done if you have signs or symptoms of diabetes. A test result of 200 mg/dl or higher suggests diabetes and should be confirmed with another diagnostic test on another day. (In fact, all the tests noted above should be confirmed on another day before making a diagnosis of diabetes or prediabetes).

Causes of Hyperglycemia

Once you've been diagnosed with type 2 diabetes, a treatment plan is put in place to lower blood sugar and keep it as close to the normal range as possible.
But even after you start treatment, you may still develop hyperglycemia at times.
When you have diabetes, it's almost impossible not to have hyperglycemia — and high blood sugar can happen for no identifiable reason. Luckily, with enough detective work, a likely cause for high blood sugar can be found.
Some of the reasons blood sugar may go too high include:

• Missing prescribed medicines or taking medication at the wrong times or in the wrong amounts
• High food intake or larger consumptions of carbohydrate than expected or intended
• Lack of sleep
• Emotional stress
• Intense exercise

Illness is another important — and common — cause of hyperglycemia. The stress of an illness (cold or flu) or infection can cause your body to release stress hormones, which raise blood sugar.
So even if you aren't eating much because you feel sick, it's still necessary to check blood sugar levels and take diabetes medicines.
You should also ask your doctor about how to take your diabetes medications if you aren't eating properly. You may develop hypoglycemia (low blood sugar) if you keep taking your medication without eating right — especially sulfonylureas such as glipizide (Glucotrol), glyburide (Micronase, Glynase, and Diabeta), and glimepiride (Amaryl).
You may need to use insulin temporarily during an illness, even if it's not part of your usual diabetes regimen.
This is why it's especially important to work with your diabetes care team to develop a sick-day plan, which includes instructions and supplies for checking blood sugar levels, taking medicines and calling for help when necessary.

When Hyperglycemia Is a Medical Emergency

Extreme hyperglycemia can lead to hyperosmolar hyperglycemic state (HHS), which is a medical emergency that must be treated in a hospital.
In HHS, the blood sugar level exceeds 600 mg/dl and may reach as high as 2,000 mg/dl. The very high blood sugar level is accompanied by dehydration, and the blood literally becomes thick, as the sugar concentration rises and the water content decreases.

HHS usually develops over several days or even weeks. It can be prevented by checking your blood sugar level regularly and by treating very high levels by taking rapid-acting insulin and drinking water.

Sources

• Christopher D. Saudek, Richard R. Rubin, and Thomas W. Donner (2014). The Johns Hopkins Guide To Diabetes.
• When You’re Sick; American Diabetes Association.
• Kitabchi et al. (2006). “Hyperglycemic Crises in Adult Patients With Diabetes.” Diabetes Care.

Type 2 Diabetes Symptoms

• By Ingrid Strauch
• Medically Reviewed by Sanjai Sinha, MD

Fatigue, increased thirst, irritability, and hunger – type 2 diabetes causes many symptoms that can be mistaken for other conditions.

Because type 2 diabetes develops slowly, and symptoms generally come on gradually, they may go unnoticed for a long time, or they may be attributed to something else.
For example, increased thirst may be chalked up to a hot summer, or fatigue may be interpreted as a sign of aging or stress.
This is unfortunate, because even short-term high blood sugar diminishes your quality of life. And if high blood sugar persists for a long time, it can eventually cause complications such as eye or kidney disease that cannot be completely reversed with improved blood sugar control.
Type 2 diabetes can cause a wide range of signs and symptoms, including:

• Fatigue
• Dry mouth
• Thirst
• Excessive urination
• Hunger
• Weight loss
• Blurry vision
• Cloudy thinking
• Irritability
• Wounds that won't heal

Frequent infections may also be a sign of type 2 diabetes. In women, vaginal yeast infections are particularly common. Yeast infections can also occur on the skin and, in men, in the groin.
Other infections associated with undiagnosed type 2 diabetes include gum infections, urinary tract infections (particularly in women), slowly healing wounds with subsequent infections, and infections of the feet.

Symptoms in Men

Type 2 diabetes symptoms are generally the same for men and women.
However, urological problems such as erectile dysfunction (ED) — the inability to achieve or maintain an erection — have been associated with all forms of diabetes, including type 2.
According to the National Diabetes Information Clearinghouse, 20 to 75 percent of men with any type of diabetes have ED.
Researchers believe diabetes causes sexual function problems in men due to damage to the body's autonomic nervous system (ANS), which controls circulation.
If you have the symptoms of ED, it may be a sign you have diabetes.

Another urological problem associated with diabetes in men is retrograde ejaculation, or the release of semen into the bladder during ejaculation. Symptoms include reduced semen during ejaculation.

Symptoms in Women

Women with type 2 diabetes are at increased risk for vaginal yeast infections.
This is because type 2 diabetes has been associated with increased yeast in the vaginal area.
Experts believe these vaginal infections will also lead to urinary tract and bladder infections, as both yeast and bacteria multiply when blood sugar is elevated.

What Causes Type 2 Diabetes Symptoms?

All of the signs and symptoms of type 2 diabetes are caused by high blood sugar and/or insufficient insulin:

Excessive urination (polyuria): When the concentration of glucose in the blood rises above normal levels, your body attempts to dilute your blood by pulling fluid into your bloodstream. At the same time, the high level of glucose in the fluid entering your kidneys causes them to discharge large amounts of glucose as urine, rather than reabsorbing it into the body as they normally would. These two processes together result in large amounts of fluid being lost through urination.

Thirst (polydipsia): As the amount of urine being excreted increases, your body starts to feel
dehydrated, prompting you to feel thirsty and drink more. If you reach for sugary drinks to quench your thirst, the problem becomes worse.

Dry mouth: Dry mouth goes hand in hand with increased thirst, as high blood sugar and excessive urination dehydrate your body.

Fatigue: Normally insulin allows glucose into the cells, where it's used to fuel cellular functions and stored for future energy needs. If there is not enough insulin, not much glucose gets into your cells, and your body is literally “running on empty.” In addition, if excessive urination is interrupting your sleep, you may feel fatigued from lack of sleep.

Hunger (polyphagia): Similar to fatigue, hunger is caused when the glucose from food stays in your bloodstream rather than being transported to your cells where it's needed for fuel. Eating more food doesn't help and, in fact, makes things worse by raising your blood sugar levels even higher.

Weight loss: When large amounts of glucose are being excreted in your urine, the calories that that glucose would have provided are being lost as well. The effect is the same as consuming fewer calories in the first place.

Blurry vision: Normally, the lens of your eye changes shape as you focus on objects that are nearby
or far away. But when your blood sugar is high, your lens becomes swollen and unable to change shape to focus.

Infections: The bacteria and fungi that cause infections thrive on sugar, so more sugar means more food for them. In addition, high blood sugar slows blood circulation, meaning infection-fighting white blood cells can't get to where they're needed as quickly.

Wounds that won't heal: High blood sugar impairs parts of your immune system that are needed for fighting infections and healing wounds. Wounds also need oxygen to heal, and any slowdown in your blood circulation slows oxygen delivery throughout your body.

Cloudy thinking: Your brain uses a lot of glucose to fuel its various functions, and when it can't get that glucose (because of insufficient insulin), the result can be difficulty thinking, remembering, and staying focused. You may even become disoriented.

The good news is that bringing blood sugar levels down to normal levels can alleviate all of these signs and symptoms. And the earlier these symptoms are noticed — and the earlier a person can be tested for type 2 diabetes — the better!

 

Sources

• Dubois (2012). “High Blood Glucose: What’s Behind the Symptoms?” Diabetes Self-Management.
• “Am I at risk for type 2 diabetes? Taking Steps to Lower Your Risk of Getting Diabetes.” National Diabetes Information Clearinghouse.
• Type 2 Diabetes; Mayo Clinic.
• Sexual and Urologic Problems of Diabetes; National Institute of Diabetes and Digestive and Kidney Diseases.