Medically reviewed on Jan 21, 2018 by L. Anderson, PharmD.
What is Diabetes?
Diabetes is a chronic, long-term disease marked by high levels of sugar in the blood. It can be caused by too little or no insulin (a hormone produced by the pancreas to regulate blood sugar), resistance to insulin (when cells in the body cannot effectively use insulin), or both. Diabetes can lead to serious health complications including heart disease, blindness, kidney failure, and lower-extremity amputations, such as a foot or lower leg.
Type 1 diabetes is thought to be caused by inherited and environmental risk factors. In Type 1, which is often diagnosed in children, autoimmune beta-cell destruction in the pancreas leads to absolute insulin deficiency. Prediabetes and type 2 diabetes also appear to be linked to genetic and environmental risk factors, as well as lifestyle issues such as being overweight or obese. In Type 2 diabetes, progressive loss of beta-cell insulin secretion combined with insulin resistance leads to disease. If caught early enough with screening, and combined with appropriate diet, exercise, and lifestyle changes, prediabetes can be reversible. In the U.S., being overweight or obese is the most common modifiable risk factor for type 2 diabetes; however, not all patients with type 2 diabetes have weight problems.
The American Diabetes Association (ADA), based on the 2018 guidelines, recommends routine screening for type 2 diabetes beginning at age 45 in those without risk factors. In people with body mass index (BMI) ≥25 kg/m2 and one or more additional risk factor for diabetes, screening should include the A1C, fasting plasma glucose, or two-hour oral glucose tolerance test (OGTT). Patients with prediabetes (A1C ≥5.7%, impaired glucose tolerance or impaired fasting glucose) should be tested yearly. Women who were diagnosed with gestational diabetes should have lifelong testing at least every 3 years. The test should be repeated every three years if the results are normal, dependent upon the risk status of the patient.
In 2018, the ADA also recommends that testing for prediabetes should be considered in children and adolescents who are overweight or obese (BMI >85th percentile for age and sex, weight for height >85th percentile, or weight >120% of ideal for height) and who have additional risk factors for diabetes.
Risk Factors for Type 2 Diabetes
- age ≥45 years
- overweight (body mass index [BMI] ≥25 kg/m2) or obese (BMI ≥30 kg/m2)
- a family history of type 2 diabetes
- sedentary, inactive lifestyle
- high risk due to ethnicity (e.g., African American, Latino, Native American, Asian American, Pacific Islander)
- a previous history of gestational diabetes
- A1C ≥5.7%, impaired glucose tolerance (IGT) or impaired fasting glucose (IFG)
- history of polycystic ovary syndrome
- HDL cholesterol <35 mg/dL or triglycerides >250 mg/dL
- blood pressure over 140/90 mm/Hg or receiving blood pressure treatment
- history of vascular disease
- conditions suggestive of insulin resistance i.e., (acanthosis nigricans, severe obesity)
Every 21 seconds someone in the U.S. is diagnosed with diabetes. As of 2015, 30.3 million people -- 9.4% of the population -- have diabetes, with about 1.25 million American children and adults having type 1 diabetes. Shockingly, about 7.2 million people with diabetes are currently undiagnosed. Roughly 84 million people have prediabetes, when blood glucose levels are higher than normal but not yet high enough to be diagnosed as diabetes. Long-term damage to the heart and circulatory system can still occur with prediabetes. Diabetes is the seventh leading cause of death in the United States, as reported by the ADA.
The prevalence of diabetes is greater among older people. Among Americans aged 65 years or older, 25.2% (12 million seniors) have diabetes (diagnosed or undiagnosed).
The ADA states that the total costs of prediabetes and diabetes in the U.S. are roughly $322 billion according to the latest statistics. Treating diabetes has soared; the average price of insulin nearly tripled between 2002 and 2013.
Causes of Diabetes
To understand diabetes, it is important to first understand the normal process of food metabolism. Several things happen when food is digested:
- A sugar called glucose enters the bloodstream. Glucose is a source of fuel for the body.
- An organ called the pancreas, which lies close to the stomach, makes insulin. The role of insulin is to move glucose from the bloodstream into muscle, fat, and liver cells, where it can be used as fuel.
People with diabetes have high blood glucose because their pancreas does not make enough insulin or their muscle, fat, and liver cells do not respond to insulin normally (insulin resistance), or both.
There are three major types of diabetes:
- Type 1 diabetes is usually diagnosed in childhood. The beta cell of the pancreas makes little or no insulin, and daily injections of insulin are required to sustain life. Without proper daily management, medical emergencies can arise. Type 1 diabetes was previously known as insulin-dependent diabetes mellitus (IDDM) or juvenile diabetes.
- Type 2 diabetes is far more common than type 1 and makes up 90% or more of all cases of diabetes. Type 2 diabetes was formerly called adult-onset diabetes or noninsulin-dependent diabetes. It usually occurs in adulthood, although more cases are now occurring in children. Here, the pancreas does not make enough insulin to keep blood glucose levels normal, often because the body does not respond well to the insulin. Many people with type 2 diabetes do not know they have it, although it is a serious condition. Type 2 diabetes is becoming more common due to the growing number of older Americans, increasing obesity, and failure to exercise.
- Gestational diabetes is high blood glucose that develops at the late stages of pregnancy in a person who does not have diabetes. Although gestational diabetes usually goes away after the baby is born, a woman may be at greater risk of developing type 2 diabetes later in life. Gestational diabetes can be caused by hormones or lack of insulin.
Risk Factors for Diabetes
Type 1 Diabetes Risk Factors
- Genetics and family history
- The presence of autoantibodies in which the insulin-producing cells are attacked
- Environmental factors or possible virus exposure
- Caucasian race
- Finnish and Swedish people seem to have a higher risk for Type 1 diabetes
Type 2 Diabetes Risk Factors (How Do You Get Type 2 Diabetes?)
- A parent, brother, or sister with diabetes
- Age greater than 45 years
- Some ethnic groups (particularly African-Americans and Hispanic Americans)
- Gestational diabetes or delivering a baby weighing more than 9 pounds (4 kilograms)
- High blood pressure
- High blood levels of triglycerides (a type of fat molecule)
- High blood cholesterol level
- Physical inactivity
Gestational Diabetes Risk Factors
- Age older than 25 years
- Previous history of gestational diabetes
- Close family member with Type 2 diabetes
- Current prediabetes
- Currently overweight
- Nonwhite race
- Polycystic ovary syndrome (PCOS)
As previously mentioned, the American Diabetes Association recommends that all adults be screened for diabetes at least every three years. A person at high risk should be screened more often.
Research shows that you can lower your risk for type 2 diabetes by 58% by:
- Losing 7% of your body weight (roughly 15 pounds if you weigh 200 pounds)
- Engaging in moderate exercise (such as brisk walking) 30 minutes a day, five days a week
Symptoms of Diabetes
High blood levels of glucose can cause several symptoms, including frequent urination, excessive thirst, hunger, fatigue, weight loss, and blurry vision. However, because type 2 diabetes develops slowly, some people with high blood sugar experience no symptoms at all.
Symptoms of Type 1 Diabetes:
- Increased thirst
- Increased urination
- Weight loss in spite of increased appetite
Symptoms of Type 2 Diabetes:
- Increased thirst
- Increased urination
- Increased appetite
- Blurred vision
- Slow-healing infections
- Impotence in men
Symptoms of Gestational Diabetes
- Usually no noticeable symptoms
- Rarely may have increased thirst or urination
- Typically you will find out that you have gestational diabetes through a routine glucose challenge test given between 24 and 28 weeks of pregnancy
Exams and Tests
A urinalysis may be used to look for glucose and ketones from the breakdown of fat. However, a urine test alone does not diagnose diabetes. The following blood glucose tests are used to diagnose diabetes:
- Hemoglobin A1C test (HbA1C) -- The A1C test measures the average blood glucose for the last 2 to 3 months. An A1C level of 6.5 percent or higher yields a diagnosis of diabetes. Prediabetes is diagnosed with a result between 5.7 and 6.4 percent, which indicates a high risk of developing diabetes. Normal levels are below 5.7 percent.
- Fasting blood glucose level (FBG) -- diabetes is diagnosed if higher than 126 mg/dL on two occasions. Levels between 100 and 126 mg/dL (7.0 mmol/L) are referred to as impaired fasting glucose or pre-diabetes. Fasting is defined as no caloric intake for at least 8 hours. These levels are considered to be risk factors for type 2 diabetes and its complications.
- Oral glucose tolerance test (OGTT) -- diabetes is diagnosed if glucose level is higher than 200 mg/dL (11.1 mmol/L) after 2 hours following the consumption of a sugar drink known as the oral glucose tolerance test (OGTT). This test is used more often for the diagnosis of type 2 diabetes.
- In the absence of unequivocal hyperglycemia (the patient is borderline hyperglycemic), the result should be confirmed by repeat testing for the above three tests.
- Random (non-fasting) blood glucose level -- diabetes is suspected if higher than 200 mg/dL (11.1 mmol/L) and accompanied by the classic symptoms of increased thirst, urination, fatigue, hunger and weight loss. This test must be confirmed with a fasting blood glucose test. In patients who do not have diabetes symptoms, and whose random serum glucose level is over 140 mg/dL, a FPG or HbA1c level should be measured. An FPG level of 100-125 mg/dL is considered an impaired fasting glucose (IFG).
Patients with type 1 diabetes usually develop symptoms over a short period of time, and the condition is often diagnosed in an emergency setting. In addition to having high glucose levels, acutely ill type 1 diabetics have high levels of ketones.
Ketones are produced by the breakdown of fat and muscle, and they are toxic at high levels. Ketones in the blood cause a condition called "acidosis" (low blood pH) or (diabetic ketoacidosis). Urine testing detects both glucose and ketones in the urine. Blood glucose levels are also high.
There is no cure for diabetes. The immediate goals are to stabilize your blood sugar and eliminate the symptoms of high blood sugar. The long-term goals of treatment are to prolong life, relieve symptoms, and prevent long-term complications such as heart disease, amputations, and kidney failure.
Lifestyle changes are the cornerstone of diabetes management for all patients. In addition to medication, achieving goals for weight management and diet, physical activity, smoking cessation, and moderate alcohol use is imperative for diabetes control.
Bariatic weight loss surgery may be an option for patients with a BMI over 35 kg/m2 and type 2 diabetes. After surgery, patients will need lifelong lifestyle support and medical monitoring.
Diabetes Management Skills
Basic diabetes management skills will help prevent the need for emergency care. These skills include:
- How to recognize and treat low blood sugar (hypoglycemia) and high blood sugar (hyperglycemia)
- What to eat and when
- How to inject insulin, use your insulin pump, and/or take oral your medication
- How to test and record blood glucose
- How to test urine for ketones (type 1 diabetes only)
- How to adjust insulin and/or food intake when changing exercise and eating habits
- How to handle sick days
- Where to buy diabetes supplies and how to store them
After you learn the basics of diabetes care, learn how the disease can cause long-term health problems and the best ways to prevent these problems. People with diabetes need to review and update their knowledge, because new research and improved ways to treat diabetes are constantly being developed.
What Should You Eat? The Diabetes Diet
You should work closely with your health care provider to learn how much fat, protein, and carbohydrates you need in your diet. Your specific meal plans need to be tailored to your food habits and preferences. People with type 1 diabetes should eat at about the same times each day and try to be consistent with the types of food they choose. This helps to prevent blood sugars from becoming extremely high or low. Type 2 diabetics should follow a well-balanced and low-fat diet.
A registered dietician can be very helpful in planning dietary needs.
Weight management is important to achieving control of diabetes. Some people with type 2 diabetes can stop medications after losing excess weight, although the diabetes is still present.
How to Take Insulin or Oral Medication
Medications to treat diabetes include insulin and glucose-lowering pills, called oral hypoglycemic agents. People with type 1 diabetes cannot make their own insulin, so daily insulin injections or inhalations are required. People with type 2 diabetes make insulin but cannot use it effectively.
Insulin is not available in oral tablet form, although a new inhaled insulin product called Afrezza was approved in 2014. Afrezza is an ultra rapid-acting inhaled insulin that is administered with meals to improve blood sugar control in adult diabetics. Insulin is usually is delivered by injections that are required one to four times per day. Some people use an insulin pump, which is worn at all times and delivers a steady flow of insulin throughout the day.
Insulin preparations differ in how quickly they start to work and how long they remain active. Sometimes different types of insulin are mixed together in a single injection. The types of insulin to use, the doses required, and the number of daily injections are chosen by a health care professional trained to provide diabetes care.
People who need insulin are taught to give themselves injections by their health care providers or diabetes educators. Special insulin pens are also available for some insulins that prevent the need for pulling up insulin with a needle into a syringe. The insulin is stored in the pen and needles can be attached to the pens prior to injection.
Unlike type 1 diabetes, type 2 diabetes may respond to treatment with exercise, diet, and/or oral medications. There are several oral hypoglycemic agents that lower blood glucose in type 2 diabetes. Selection of an oral diabetes treatment may follow this general guideline:
- Glucophage or Glucophage XR (metformin), in the class biguanides, is the recommended first-line oral treatment for type 2 diabetes by the American Diabetes Association (ADA). Metformin does not cause weight gain or elevate insulin levels. Metformin reduces hyperglycemia by decreasing liver gluconeogenesis (sugar production), decreases glycogenolysis (the breakdown of glycogen to glucose-1-phosphate and glucose) and increases sensitivity to insulin. Avandia (rosiglitazone) and Actos (pioglitazone) are thiazolidinediones that also work by increasing insulin sensitivity.
- Medications that increase insulin production by the pancreas are called insulin secretagogues and may be added to therapy if metformin and lifestyle measures do not adequately reduce blood sugar, or may be started individually if metformin is not tolerated. These include drugs from the class known as sulfonylureas such as Amaryl (glimepiride), Glucotrol and Glucotrol XL (glipizide), or Diabeta and Glynase (glyburide). Glyburide can lead to significant hypoglycemia and may not be the best first choice sulfonylurea. Glimepiride may be a better choice in many situations due to a lower risk of hypoglycemia.
- Prandin (repaglinide) and Starlix (nateglinide) are in the drug class known as meglitinides and can be used in place of sulfonylureas if they are not tolerated. These agents may also lead to hypoglycemia.
- Other drug classes that can be used in the treatment of type 2 diabetes include the thiazolidinediones such as Avandia (rosiglitazone) and Actos (pioglitazone); the DPP-4 inhibitors, which include Januvia (sitagliptin), Onglyza (saxagliptin), Tradjenta (linagliptin), Nesina (alogliptin); the SGLT-2 inhibitors like Invokana (canagliflozin), Farxiga (dapagliflozin), Invokamet (canagliflozin/metformin), and Jardiance (empagliflozin). Another class, known as the glucagon-like peptide-1 (GLP-1) receptor agonists (or incretin mimetics), are subcutaneously injected agents that include Tanzeum (albiglutide), Byetta (exenatide), and Victoza (liraglutide).
- For most patients, metformin (Glucophage, Glucophage XR) will be initial therapy, but insulin may be required short-term for patients who present with excessively high blood sugar. Metformin is a preferred initial drug therapy because it rarely leads to weight gain or hypoglycemia (low blood sugar), is available generically and therefore is cost- effective, and has been shown to have a positive effect on LDL cholesterol.
- Different groups of oral medications may be combined, or insulin and oral medications may be used together. Blood thinners such as aspirin or clopidogrel may be started in patients at higher risk for cardiovascular events such as stroke or heart attack. Other medications such as blood pressure control or high cholesterol treatments may be needed, as well. Angiotensin converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs) will be started in diabetic patients with protein in their urine to help protect the kidneys and other organs.
- Most type 2 diabetics will require more than one medication for good blood sugar control within three years of starting their first medication. The American Diabetes Association recommends the use of insulin in patients who do not reach their blood sugar goals with the use of two oral agents.
Some people with type 2 diabetes find they no longer need medication if they lose weight and increase activity, because when their ideal weight is reached, their own insulin and a careful diet can control their blood glucose levels. Even a 10-15 percent weight loss in some diabetic patients can drastically lower blood sugar.
Oral hypoglycemic agents are not known to be safe for use in pregnancy; women who have type 2 diabetes and take these medications may be switched to insulin during pregnancy and while breast-feeding.
Gestational diabetes is treated with diet and insulin.
Self-monitoring of blood glucose is done by checking the glucose content of a drop of blood. Regular testing tells you how well diet, medication, and exercise are working together to control your diabetes.
The results of the test can be used to adjust meals, activity, or medications to keep blood sugar levels in an appropriate range. Testing provides valuable information for the health care provider and identifies high and low blood sugar levels before serious problems develop.
The American Diabetes Association recommends that premeal blood sugar levels fall in the range of 80 to 120 mg/dL and bedtime blood levels fall in the range of 100 to 140 mg/dL. Your doctor may adjust this depending on your circumstances.
You should also ask your doctor how often you need to have your hemoglobin A1c (HbA1c) level checked. The HbA1c is a measure of average blood glucose during the previous two to three months. It is a very helpful way to monitor a patient's overall response to diabetes treatment over time. A person without diabetes has an HbA1c around 5%. People with diabetes should try to keep it below 7%. Usually HbA1c is checked every three months.
Ketone testing is another test that is used in type 1 diabetes. Ketones build up in the blood when there is not enough insulin in people with type 1 diabetes, eventually "spilling over" into the urine. The ketone test is done on a urine sample. High levels of blood ketones may result in a serious condition called ketoacidosis. Ketone testing is usually done at the following times:
- When the blood sugar is higher than 240 mg/dL
- During acute illness (for example, pneumonia, heart attack, or stroke)
- When nausea or vomiting occur
- During pregnancy
Another complication that can be avoided by checking the blood sugar level is Hyperosmolar Hyperglycemic Nonketotic Syndrome (HHNS). HHNS is a serious condition usually seen in older persons with type 2 diabetes, although it can occur in type 1 patients also. HHNS is usually brought on by an illness or infection. HHNS only occurs when diabetes is uncontrolled. HHNS may occur gradually, and take days or even weeks to develop. The best way to avoid HHNS is to check your blood sugar regularly. Be aware of the symptoms of HHNS that include:
- Blood sugar level over 600 mg/dL
- Dry mouth
- Excessive urination
- Dark colored urine
- Extreme thirst
- Warm, dry skin that does not sweat
- High fever (over 101 degrees Fahrenheit)
- Sleepiness or confusion
- Loss of vision
- Hallucinations (seeing or hearing things that are not there)
- Weakness on one side of the body
Regular exercise is especially important for people with diabetes. It helps with blood sugar control, weight loss, and high blood pressure. People with diabetes who exercise are less likely to experience a heart attack or stroke than diabetics who do not exercise regularly. You should be evaluated by your physician before starting an exercise program.
Here are some exercise considerations:
- Choose an enjoyable physical activity that is appropriate for your current fitness level.
- Exercise every day, and at the same time of day, if possible.
- Monitor blood glucose levels before and after exercise.
- Carry food that contains a fast-acting carbohydrate in case you become hypoglycemic during or after exercise.
- Carry a diabetes identification card and a mobile phone or change for a payphone in case of emergency.
- Drink extra fluids that do not contain sugar before, during, and after exercise.
Changes in exercise intensity or duration may require changes in diet or medication dose to keep blood sugar levels from going too high or low.
People with diabetes are prone to foot problems because of the likelihood of damage to blood vessels and nerves and a decreased ability to fight infection. Problems with blood flow and damage to nerves may cause an injury to the foot to go unnoticed until infection develops. Death of skin and other tissue can occur.
If left untreated, the affected foot may need to be amputated. Diabetes is the most common condition leading to amputations.
To prevent injury to the feet, people with diabetes should adopt a daily routine of checking and caring for the feet as follows:
- Check your feet every day, and report sores or changes and signs of infection.
- Wash your feet every day with lukewarm water and mild soap, and dry them thoroughly.
- Soften dry skin with lotion or petroleum jelly.
- Protect feet with comfortable, well-fitting shoes.
- Exercise daily to promote good circulation.
- See a podiatrist for foot problems or to have corns or calluses removed.
- Remove shoes and socks during a visit to your health care provider and remind him or her to examine your feet.
- Stop smoking, which hinders blood flow to the feet.
For additional information, see diabetes resources.
The risks of long-term complications from diabetes can be reduced.
The Diabetes Control and Complications Trial (DCCT) studied the effects of tight blood sugar control on complications in type 1 diabetes. Patients treated for tight blood glucose control had an average HbA1c of approximately 7%, while patients treated less aggressively had an average HbA1c of about 9%. At the end of the study, the tight blood glucose group had dramatically fewer cases of kidney disease, eye disease, and nervous system disease than the less-aggressively treated patients.
In the United Kingdom Prospective Diabetes Study (UKPDS), researchers followed nearly 4,000 people with type 2 diabetes for 10 years. The study monitored how tight control of blood glucose (HbA1c of 7% or less) and blood pressure (less than 144 over less than 82) could protect a person from the long-term complications of diabetes.
This study found dramatically lower rates of kidney, eye, and nervous system complications in patients with tight control of blood glucose. In addition, there was a significant drop in all diabetes-related deaths, including lower risks of heart attack and stroke. Tight control of blood pressure was also found to lower the risks of heart disease and stroke.
The results of the DCCT and the UKPDS dramatically demonstrate that good blood glucose and blood pressure control, many of the complications of diabetes can be prevented.
Emergency complications include diabetic hyperglycemic hyperosmolar coma.
Long-term complications include:
- Diabetic retinopathy
- Diabetic nephropathy
- Diabetic neuropathy
- Peripheral vascular disease
- Hyperlipidemia, hypertension, atherosclerosis, and coronary artery disease
When to Contact a Medical Professional
Go to the emergency room or call the local emergency number (such as 911) if symptoms of ketoacidosis occur:
- Increased thirst and urination
- Deep and rapid breathing
- Abdominal pain
- Sweet-smelling breath
- Loss of consciousness
Go to the emergency room or call the local emergency number if symptoms of extremely low blood sugar (hypoglycemic coma or severe insulin reaction) occur:
- Double vision
- Lack of coordination
- Convulsions or unconsciousness
Prevention of Diabetes
Maintaining an ideal body weight and an active lifestyle may prevent the onset of type 2 diabetes. Currently there is no way to prevent type 1 diabetes.
- Diabetes Risk Factors & Prevention
- Diabetes Symptoms & Complications
- Diabetes Treatment
- One Touch Ultra
- OneTouch Blood Glucose Monitors
- Top 6 Breakthrough Diabetes Treatments You May Have Missed
- American Diabetes Association (ADA). Standards of Medical Care in Diabetes - 2018. Diabetes Care 2018 Jan; 41(Supplement 1): S1-S2. Accessed Jan. 21, 2018 at https://care.diabetesjournals.org/content/diacare/suppl/2017/12/08/41.Supplement_1.DC1/DC_41_S1_Combined.pdf
- McCulloch DK, Hayward RA, et al. Screening for type 2 diabetes mellitus. Up to Date. Aug. 7, 2017. Accessed Jan. 21, 2018 at https://www.uptodate.com/contents/screening-for-type-2-diabetes-mellitus#H18058884
- American Diabetes Association (ADA). The Staggering Costs of Diabetes. (infographic). Accessed Jan. 21, 2018 at http://www.diabetes.org/assets/pdfs/basics/cost-of-diabetes-2017.pdf
- American Diabetes Association. Diabetes Pro. Clinical Practice Recommendations. Standards of Medical Care in Diabetes 2013 - Slide presentation. Accessed June 26, 2013. http://professional.diabetes.org/ResourcesForProfessionals.aspx?cid=84160
- Centers for Disease Control (CDC). Diabetes Public Health Resource. Diabetes Research and Statistics. Accessed June 26, 2013. http://www.cdc.gov/diabetes/data/index.html
- Centers for Disease Control and Prevention. National diabetes fact sheet: national estimates and general information on diabetes and prediabetes in the United States, 2011. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, 2011.
- Mayo Clinic. Type 2 Diabetes. Accessed June 26, 2013. Updated Jan. 25, 2013.
- National Diabetes Information Clearinghouse. Your guide to diabetes: Type 1 and type 2. National Institute of Diabetes and Digestive and Kidney Diseases. Accessed June 26, 2013. http://diabetes.niddk.nih.gov/dm/pubs/type1and2/index.htm