Skip to Content
Is your type 2 diabetes treatment the right match?
Harvard Health Publications

Type 2 Diabetes Mellitus

What Is It?

Type 2 diabetes is a chronic disease. It is characterized by high levels of sugar in the blood. Type 2 diabetes is also called type 2 diabetes mellitus and adult-onset diabetes. That's because it used to start almost always in middle- and late-adulthood. However, more and more children and teens are developing this condition. Type 2 diabetes is much more common than type 1 diabetes, and is really a different disease. But it shares with type 1 diabetes high blood sugar levels, and the complications of high blood sugar.

During digestion, food is broken down into basic components. Carbohydrates are broken down into simple sugars, primarily glucose. Glucose is a critically important source of energy for the body's cells. To provide energy to the cells, glucose needs to leave the blood and get inside the cells.

Insulin traveling in the blood signals the cells to take up glucose. Insulin is a hormone produced by the pancreas. The pancreas is an organ in the abdomen. When levels of glucose in the blood rise (for example, after a meal), the pancreas produces more insulin.

Type 2 diabetes occurs when your body's cells resist the normal effect of insulin, which is to drive glucose in the blood into the inside of the cells. This condition is called insulin resistance. As a result, glucose starts to build up in the blood.

In people with insulin resistance, the pancreas "sees" the blood glucose level rising. The pancreas responds by making extra insulin to maintain a normal blood sugar. Over time, the body's insulin resistance gets worse. In response the pancreas makes more and more insulin. Finally, the pancreas gets "exhausted". It cannot keep up with the demand for more and more insulin. It poops out. As a result, blood glucose levels start to rise.

Type 2 Diabetes Mellitus

Type 2 diabetes runs in families. Obesity greatly increases the risk of diabetes.

Symptoms

The symptoms of diabetes are related to high blood glucose levels. They include:

  • Excessive urination, thirst and hunger

  • Weight loss

  • Increased susceptibility to infections, especially yeast or fungal infections

Extremely high blood sugar levels also can lead to a dangerous complication called hyperosmolar syndrome. This is a life-threatening form of dehydration. In some cases, hyperosmolar syndrome is the first sign that a person has type 2 diabetes. It causes confused thinking, weakness, nausea and even seizure and coma.

The treatment of type 2 diabetes also can produce symptoms. Too much glucose-lowering medicine, relative to dietary intake, can lead to the complication of low blood sugar (called hypoglycemia). Symptoms of hypoglycemia include:

  • Sweating

  • Trembling

  • Dizziness

  • Hunger

  • Confusion

  • Seizures and loss of consciousness (if hypoglycemia is not recognized and corrected)

You can correct hypoglycemia by eating or drinking something that has carbohydrates. This raises your blood sugar level.

Type 2 diabetes affects all parts of the body. It can cause serious, potentially life-threatening complications. These include:

  • Atherosclerosis — Atherosclerosis is fat buildup in the artery walls. This can impair blood flow to the all the organs. The heart, brain and legs are most often affected.

  • Retinopathy — Tiny blood vessels in the retina (the back of the eye that sees light) can become damaged by high blood sugar. The damage can block blood flow to the retina, and can lead to bleeding into the retina. Both damage the ability of the retina to see light. Caught early, retinopathy damage can be minimized by tightly controlling blood sugar and using laser therapy. Untreated retinopathy can lead to blindness.

  • Neuropathy — This is nerve damage. The most common type is peripheral neuropathy. The nerves to the legs are damaged first, causing pain and numbness in the feet. This can advance to cause symptoms in the legs and hands. Damage to the nerves that control digestion, sexual function and urination can also occur.

  • Foot problems — Sores and blisters on the feet occur for two reasons:

    • If peripheral neuropathy causes numbness, the person may not feel irritation in the foot. The skin can break down, form an ulcer, and the ulcer can get infected.

    • Blood circulation can be poor, leading to slow healing. Left untreated, a simple sore can become infected and very large. If medical treatment cannot heal the sore, an amputation may be required.

  • Nephropathy — Damage to the kidneys. This is more likely if blood sugars remain elevated and high blood pressure is not treated aggressively.

Diagnosis

Diabetes is diagnosed by testing the blood for sugar levels. Blood is tested in the morning after you have fasted overnight.

Typically, the body keeps blood sugar levels between 70 and 100 milligrams per deciliter (mg/dL), even after fasting. If a blood sugar level after fasting is greater than 125 mg/dL, diabetes is diagnosed.

Your doctor will examine you to look for:

  • Obesity, especially abdominal obesity—a condition that greatly raises a person's risk for type 2 diabetes.

  • High blood pressure—a condition often present in people with type 2 diabetes, that together with diabetes greatly increases the risk of heart disease and strokes.

  • Deposits of blood, or puffy yellow spots in the retina of your eyes—complications of both diabetes and high blood pressure, that increase the risk of blindness

  • Decreased sensation in the legs—which can cause a person with diabetes to fail to notice developing foot sores, particularly sores on the underside of the feet

  • Weak pulses in the feet—a condition that can slow or prevent the healing of foot sores, and possibly lead to amputation

  • Blisters, ulcers or infections of the feet

Laboratory tests are also used routinely to evaluate diabetes. These include:

  • Fasting plasma glucose (FPG) test. Blood is taken in the morning after fasting overnight. Normally, blood sugar levels remain between 70 and 100 milligrams per deciliter (mg/dL). Diabetes is diagnosed if a fasting blood sugar level is 126 mg/dL or higher.

  • Oral glucose tolerance test (OGTT). Blood sugar is measured two hours after drinking 75 grams of glucose. Diabetes is diagnosed if the 2-hour blood sugar level is 200 mg/dL or higher.

  • Random blood glucose test. A blood sugar of 200 mg/dL or greater at any time of day combined with symptoms of diabetes is sufficient to make the diagnosis.

  • Hemoglobin A1C (glycohemoglobin). This test measures the average glucose level over the prior two to three months. Diabetes is diagnosed if the hemoglobin A1C level is 6.5% percent or higher.

  • Blood creatinine and urine microalbumin. Tests for evidence of kidney disease.

  • Lipid profile. Measures levels of triglycerides and total, HDL, and LDL cholesterol. This evaluates the risk of atherosclerosis. People with diabetes who also have high levels of total cholesterol or LDL cholesterol are at greatly increased risk for heart disease and strokes.

Expected Duration

Diabetes is a lifelong illness. However, people with type 2 diabetes can sometimes restore their blood sugar levels to normal just by eating a healthy diet, regularly exercising, and losing weight.

Aging and episodic illness can cause the body's insulin resistance to increase. As a result, additional treatment typically is required over time.

Prevention

If a close relative—particularly, a parent or sibling—has type 2 diabetes, or if your blood glucose test shows "pre-diabetes"—defined as blood glucose levels between 100 and 125 mg/dL—you are at increased risk for developing type 2 diabetes. You can help to prevent type 2 diabetes by:

  • Maintaining your ideal body weight.

  • Exercising regularly—like a brisk walk of 1-2 miles in 30 minutes—at least five times a week, even if that does not result in you achieving an ideal weight. That's because regular exercise reduces insulin resistance, even if you don't lose weight.

  • Eating a healthy diet.

  • Taking medication. The medication metformin (Glucophage) offers some additional protection for people with pre-diabetes.

If you already have type 2 diabetes, you can still delay or prevent complications:

  • Keep tight control of your blood sugar. This reduces the risk of most complications.

  • Lower your risk of heart-related complications by:

    • Taking a daily aspirin—particularly if you already have some signs of heart disease.

    • Aggressively managing other risk factors for atherosclerosis, such as:

      • High blood pressure

      • High cholesterol and triglycerides

      • Cigarette smoking

      • Obesity

  • Visit an eye doctor and a foot specialist every year to reduce eye and foot complications.

Treatment

Diet and Exercise

In most cases, type 2 diabetes treatment begins with weight reduction through diet and exercise. A healthy diet for a person with diabetes is:

  • Low in saturated fats and cholesterol

  • Without any trans fats

  • Low in total calories

  • Nutritionally balanced with abundant amounts of:

    • Whole-grain foods

    • Monounsaturated oils

    • Fruits and vegetables

A daily multivitamin is recommended for most people with diabetes.

For some people, type 2 diabetes can be controlled just with diet and exercise. Even if medications are required, diet and exercise remain important for controlling diabetes.

Medications: Pills

The medications used for type 2 diabetes include pills and injections. The pills work in many different ways. They include medications that:

  • Reduce insulin resistance in the muscles and liver.

  • Increase the amount of insulin made and released by the pancreas.

  • Cause a burst of insulin release with each meal.

  • Delay the absorption of sugars from the intestine.

  • Slow your digestion.

  • Reduce your appetite for large meals.

  • Decrease the conversion of fat to glucose. These medications are called thiazolidinediones. One medication in this group has recently been linked to heart disease. As a result, drugs from this group are not recommended as a first choice in treatment.

Insulins

Because type 2 diabetes develops when the pancreas cannot make enough insulin to overcome insulin resistance, about one of three people with this disease take some form of insulin injection.

In advanced type 2 diabetes, or for people who want to tightly control glucose levels, insulin may be needed more than once per day and in higher doses.

Treatment plans that include both very long-acting insulin and very short-acting insulin are frequently the most successful for controlling blood sugar. Very short-acting insulin is used with meals, to help control the spike in blood sugar levels that occur with a meal. If a person does not eat on a regular schedule, very short-acting insulin can be particularly helpful.

Treatment Side Effects

Medications used to treat type 2 diabetes can have side effects. These vary by medication. Side effects may include:

  • Low blood sugar levels (hypoglycemia)

  • Weight gain

  • Nausea

  • Diarrhea

  • Leg swelling

  • Worsening of heart failure

  • Liver inflammation

  • Increased risk of heart attack (with one of the thiazolidinediones medicines)

  • Excessive gas and bloating

Fortunately, these side effects are uncommon, so the benefits of treatment far outweigh the risks. People with type 2 diabetes who have kidney failure should generally avoid an otherwise very effective diabetes medicine, metformin, because in such patients it can rarely cause a life-threatening buildup of lactic acid in the blood.

In addition to medicines that help control the level of blood sugar, people with type 2 diabetes often take other medicines that reduce the risk or to slow the onset of the complications of diabetes. These include medications that:

  • Slow the worsening of kidney disease—particularly drugs called angiotensin-converting enzyme (ACE) inhibitors, and angiotensin receptor blockers (ARBs).

  • Lower cholesterol. All diabetics should consider taking medication to lower their cholesterol, usually one of the statin medications.

  • Lower blood pressure. Diabetics should use medication to control high blood pressure if it can't be improved by lifestyle changes.

  • Protect against heart attacks. Most people with diabetes benefit from a daily aspirin.

When To Call a Professional

If you have diabetes, see your doctor regularly.

People with high blood sugar levels have a higher risk of dehydration. Contact your doctor immediately if you develop vomiting or diarrhea and are not able to drink enough fluids.

Monitor your blood sugar as advised by your health care team. Report any significant deviations in blood sugar levels.

Prognosis

Your treatment plan is likely to require adjustment over time. Insulin resistance increases with age. And the insulin-producing cells in the pancreas may wear out as the pancreas tries to keep up with the body's extra insulin needs.

After the first few years, the majority of people with type 2 diabetes require more than one medicine to keep their blood sugar controlled.

The prognosis in people with type 2 diabetes varies. It depends on how well an individual modifies his or her risk of complications. Heart attack, stroke and kidney disease can result in premature death. Disability due to blindness, amputation, heart disease, stroke and nerve damage may occur. Some people with type 2 diabetes become dependent on dialysis treatments because of kidney failure.

External resources

American Diabetes Association
ATTN: National Call Center
1701 N. Beauregard St.
Alexandria, VA 22311
Toll-Free: 1-800-342-2383
http://www.diabetes.org/

American Dietetic Association
120 South Riverside Plaza
Suite 2000
Chicago, IL 60606-6995
Toll-Free: 1-800-877-1600
http://www.eatright.org/

National Diabetes Information Clearinghouse
1 Information Way
Bethesda, MD 20892-3560
Phone: 301-654-3327
Toll-Free: 1-800-860-8747
Fax: 301-907-8906
http://diabetes.niddk.nih.gov/

National Institute of Diabetes & Digestive & Kidney Disorders
Office of Communications and Public Liaison
Building 31, Room 9A04
31 Center Drive, MSC 2560
Bethesda, MD 20892-2560
Phone: 301-496-4000
http://www.niddk.nih.gov/

Weight-Control Information Network
1 Win Way
Bethesda, MD 20892-3665
Phone: 202-828-1025
Toll-Free: 1-877-946-4627
Fax: 202-828-1028


Disclaimer: This content should not be considered complete and should not be used in place of a call or visit to a health professional. Use of this content is subject to specific Terms of Use & Medical Disclaimers.

Hide