The main diagnostic test for diabetes is taking a blood test to measure glucose, either when the individual has been fasting (not consuming food) or at other times of the day. Diagnostic tests are also used routinely during pregnancy to identify gestational diabetes. Some diabetes tests require obtaining a blood sample in a doctor's office.
Depending on the test used, the level of blood glucose can be affected by many factors including: eating or drinking (water is acceptable); taking medications that are known to raise blood sugar levels, such as oral contraceptives, some diuretics (water pills) and corticosteroids; or a recent injury, physical illness, or surgery that may temporarily alter blood sugar levels.
Fasting blood glucose test: Fasting blood glucose testing checks blood glucose levels after fasting for between 12-14 hours. The individual can drink water during this time, but should strictly avoid any other beverage. Individuals with diabetes may be asked to delay their diabetes medication or insulin dose until the test is completed. This test can be used to diagnose diabetes or pre-diabetes. The fasting plasma glucose (FPG) is the preferred test for diagnosing diabetes due to convenience and is most reliable when done on an empty stomach in the morning, so the presence of food and natural biorhythms do not cause fluctuations in blood sugar levels.
If the fasting glucose level is 100-125 milligrams/deciliter, the individual has a form of pre-diabetes called impaired fasting glucose (IFG), meaning that the individual is more likely to develop type 2 diabetes but does not have the condition yet. A level of 126 milligrams/deciliter or above, confirmed by repeating the test on another day, means that the individual has diabetes.
Oral glucose tolerance test: During an oral glucose tolerance test (OGTT), a high-glucose drink is given to the individual. Blood samples are checked at regular intervals for two hours. Glucose tolerance tests are used when the results of the fasting blood glucose are borderline. They are also used to diagnose diabetes in pregnancy (gestational diabetes). This test can be used to diagnose diabetes or pre-diabetes.
Random blood glucose test: Random blood glucose testing checks blood glucose levels at various times during the day. It does not matter when the individual last ate. Blood glucose levels tend to stay constant in an individual who does not have diabetes. This test, along with an assessment of symptoms, is used to diagnose diabetes.
Fructosamine testing: Doctors may measure the level of fructosamines, also known as glycated proteins, in serum or plasma to estimate average glucose levels in diabetic patients during the preceding two to three weeks. In diabetic patients, elevated blood glucose levels correlate with increased fructosamine formation. Fructosamine is formed due to a reaction between fructose and amino acid residues of proteins.
Fructosamine testing is often prescribed when changes are being made in a diabetes treatment plan and information is needed about how well the new plan is working. High levels of vitamin C (ascorbic acid), lipemia (high amount of fat in the blood), hemolysis (breakdown of RBCs), and hyperthyroidism (high levels of thyroid hormones) can interfere with test results.
Hemoglobin A1c (A1c): Hemoglobin A1c, also known as glycated hemoglobin or glycosylated hemoglobin, indicates an individual's average blood sugar control over the last two to three months. Sugar (glucose) in the bloodstream can become attached to the hemoglobin (the part of the cell that carries oxygen) in red blood cells. This process is called glycosylation. Once the sugar is attached, it stays there for the life of the red blood cell, which is about 120 days. The higher the level of blood sugar, the more sugar attaches to red blood cells. The hemoglobin A1c test measures the amount of sugar sticking to the hemoglobin in the red blood cells. A1c is formed when glucose in the blood binds irreversibly to hemoglobin to form a stable glycated hemoglobin complex. A1C values are not subject to the fluctuations that are seen with daily blood glucose monitoring. Results are given in percentages.
The American Diabetes Association (ADA) recommends A1c as the best test to find out if an individual's blood sugar is under control over time. The test should be performed every three months for insulin-treated patients, during treatment changes, or when blood glucose is elevated. For stable patients on oral agents, healthcare professionals recommended testing A1c at least twice per year. The ADA currently recommends an A1c goal of less than 7.0%. Studies have reported that there is a 10% decrease in relative risk of microvascular complications, such as diabetic nephropathy or diabetic neuropathy, for every 1% reduction in hemoglobin A1c.
Gestational diabetes diagnosis: Gestational diabetes is diagnosed based on blood glucose levels measured during the oral glucose tolerance test (OGTT). Glucose levels are normally lower during pregnancy, so the cutoff levels for diagnosis of diabetes in pregnancy are lower. Blood glucose levels are measured before a woman drinks a beverage containing glucose. Then levels are checked one, two, and three hours afterward. If a woman has two blood glucose levels meeting or exceeding any of the following numbers, she has gestational diabetes: a fasting blood glucose level of 95 milligrams/deciliter, a one-hour level of 180 milligrams/deciliter, a two-hour level of 155 milligrams/deciliter, or a three-hour level of 140 milligrams/deciliter.
Maturity-onset diabetes of the young (MODY) diagnosis: Genetic testing can help diagnose MODY, however, commercially available genetic tests for MODY are not widely available. In a MODY test a blood sample is collected, and the DNA is isolated and analyzed for mutations characteristic of MODY. Genetic testing may be helpful in selecting specific treatments for MODY, depending on the specific genetic mutation involved. Prenatal testing may also be available for diagnosis of MODY. As each type of MODY has different clinical manifestations, it is recommended for the patient to work with their healthcare provider to discuss testing options, to determine whether genetic testing is appropriate, and to decide which genetic tests are necessary.
signs and symptoms
Type 1 diabetes
Symptoms of type 1 diabetes are often dramatic and come on very suddenly. Type 1 diabetes is usually recognized in childhood or early adolescence, often in association with an illness (such as a virus) or injury. The initial symptoms of type 1 diabetes are: an increased production of urine, excessive thirst, fatigue, tiredness, loss of weight, increased appetite, feeling sick, blurred vision, and infections such as thrush or irritation of the genitals.
Type 1 diabetics can develop diabetic ketoacidosis. Ketoacidosis is a serious condition where the body has dangerously high levels of ketones. Ketones are substances that are made when the body breaks down fat for energy. Normally, the body gets the energy it needs from carbohydrates. However, stored fat is broken down and ketones are made if the diet does not contain enough carbohydrates to supply the body with sugar (glucose) for energy, or if the body cannot use blood sugar (glucose) properly, as in diabetes. Symptoms of ketoacidosis include nausea and vomiting. Dehydration and often-serious disturbances in blood levels of potassium follow. Without treatment, ketoacidosis can lead to coma and death.
Type 2 diabetes
Symptoms of type 2 diabetes are often subtle and may be attributed to aging or obesity. An individual may have type 2 diabetes for many years without knowing it. Individuals with type 2 diabetes can develop hyperglycemic hyperosmolar non-ketotic syndrome, which is characterized by no or few ketones and high glucose in the blood
Some individuals who have type 2 diabetes have patches of dark, velvety skin in the folds and creases of their bodies, usually in the armpits and neck. This condition, called acanthosis nigricans, is a sign of insulin resistance.
If not properly treated, type 2 diabetes can lead to complications such as blindness, kidney failure, heart disease, and nerve damage.
Maturity-onset diabetes of the young (MODY)
Maturity-onset diabetes of the young (MODY) may occur during childhood or adolescence, but may be misdiagnosed as Type 1 or Type 2 diabetes, or may be unidentified until the patient is an adult. Individuals with MODY may have little to no symptoms of diabetes, or have only mild symptoms, or may have mild to significant hyperglycemia. MODY patients are typically not overweight, and generally do not have similar risk factors as seen with Type 2 diabetes, such as hypertension (high blood pressure), or hyperlipidemia (elevated serum lipids).
Many patients with MODY do not have any symptoms of diabetes, and may be diagnosed with high serum glucose while in the process of discovering other disorders. Other symptoms may include increased thirst and urination. It is recommended that if an individual has mild to moderate hyperglycemia identified before the age of 30, a family history of diabetes, and low insulin requirements, that they be tested for MODY.
Common symptoms of Type 1 and Type 2 diabetes
Fatigue: In diabetes, the body is inefficient and sometimes unable to use glucose for fuel. The body switches over to metabolizing fat, partially or completely, as a fuel source. This process requires the body to use more energy. The end result is feeling fatigued or constantly tired.
Unexplained weight loss: Individuals with diabetes are unable to process many of the calories in the foods they eat. Therefore, they may lose weight even though they eat an apparently appropriate or even excessive amount of food. Losing sugar and water in the urine and the accompanying dehydration also contributes to weight loss.
Excessive thirst (polydipsia): An individual with diabetes develops high blood sugar levels. The body tries to counteract this by sending a signal to the brain to dilute the blood, which translates into thirst. The body encourages more water consumption to dilute the high blood sugar back to normal levels and to compensate for the water lost by excessive urination.
Excessive urination (polyuria): Polyuria is frequent urination. Another way the body tries to get rid of the extra sugar in the blood is to excrete it in the urine. This can also lead to dehydration because excreting the sugar carries a large amount of water out of the body along with it.
Excessive eating (polyphagia): Polyphagia is excessive hunger. If the body is able, it will secrete more insulin in order to try to deal with the excessive blood sugar levels. One of the functions of insulin is to stimulate hunger. Therefore, higher insulin levels lead to increased hunger and eating. Despite increased caloric intake, the person may gain very little weight or may even lose weight.
Poor wound healing: White blood cells are important in defending the body against bacteria and also in cleaning up dead tissue and cells. High blood sugar levels prevent white blood cells from functioning normally. When these cells do not function properly, wounds take much longer to heal and become infected more frequently.
Vascular problems: Long-term high blood sugar levels are associated with thickening of blood vessels, which prevents good circulation and body tissues from getting enough oxygen and other nutrients.
Infections: Certain infection syndromes, such as frequent yeast infections, skin infections, and frequent urinary tract infections, may result from suppression of the immune system by diabetes and by the presence of glucose in the tissues, which allow bacteria to grow well. They can also be an indicator of poor blood sugar control in a person known to have diabetes.
Altered mental status: Agitation, unexplained irritability, inattention, extreme lethargy, or confusion can all be signs of very high blood sugar, ketoacidosis, hyperosmolar hyperglycemia nonketotic syndrome, or hypoglycemia (low sugar). These merit the immediate attention of a medical professional. Call a healthcare provider or 911.
Blurry vision: The primary cause of legal blindness in the working population of the United States today is diabetes mellitus. Blurry vision is not specific for diabetes but is frequently present with high blood sugar levels.
Diabetes mellitus (diabetes) can affect many major organs in the body, including the heart, blood vessels, nerves, eyes, and kidneys. Keeping blood sugar levels close to normal most of the time can dramatically reduce the risk of these complications.
Short-term complications of diabetes, such as a high blood sugar level, require immediate care. Left untreated, these conditions can cause seizures and loss of consciousness (coma).
Hyperglycemia: Hyperglycemia is a condition of high blood sugar levels. Blood sugar levels can rise for many reasons, including eating too much, stress, or not taking enough insulin or medications. It is important to check blood sugar levels often and watch for signs and symptoms of high blood sugar, including frequent urination, increased thirst, dry mouth, blurred vision, fatigue, and nausea. If hyperglycemia is present, adjustment to meal plans, medications, or both may be necessary. If blood sugar levels are persistently above 250 mg/dL, consulting a doctor immediately is recommended by healthcare providers. Diabetic hyperosmolar syndrome, a life-threatening condition in which sky-high blood sugar causes blood to become thick and syrupy, may be present.
Diabetic ketoacidosis: Diabetic ketoacidosis is characterized by high levels of ketones in the blood. If the cells are starved for energy, the body may begin to break down fat. This produces toxic substances known as ketones. It is important to watch for loss of appetite, nausea, vomiting, fever, stomach pain, and a sweet, fruity smell on the breath, especially if the blood sugar level has been consistently higher than 250 milligrams/deciliter. Diabetic ketoacidosis is more common in type 1 diabetes than type 2.
Hypoglycemia: Hypoglycemia is a condition of low blood sugar. If blood sugar levels drop below the target range, it is known as low blood sugar. Blood sugar levels can drop for reasons including skipping a meal, getting more physical activity than normal, or taking too much diabetic medication. It is important to check blood sugar levels regularly and to watch for early signs and symptoms of low blood sugar, including sweating, shakiness, weakness, hunger, dizziness, and nausea. Later signs and symptoms include slurred speech, drowsiness, and confusion. If signs or symptoms of low blood sugar are present, it is recommended by healthcare providers to eat or drink something that will quickly raise blood sugar levels, such as fruit juice, glucose tablets, hard candy, or regular (not diet) soda. If consciousness is lost, a family member or close contact may need to give an emergency injection of glucagon, a hormone that stimulates the release of sugar into the blood. Glucagon is a medication that is prescribed to some individuals with blood sugar regulation problems.
Long-term complications of diabetes develop gradually. The earlier the individual develops diabetes and the less controlled the blood sugar levels are, the higher the risk of complications. Eventually, diabetes complications may be disabling or even life-threatening.
Heart and blood vessel disease: Diabetes dramatically increases the risk of various cardiovascular problems, including coronary artery disease with chest pain (angina), heart attack, stroke, narrowing of the arteries (atherosclerosis), and high blood pressure. According to the American Heart Association, approximately 75% of individuals who have diabetes die of some type of heart or blood vessel disease. Diabetic microangiopathy is the damage to very small blood vessels due to high blood sugar levels. Microangiopathy causes the walls of very small blood vessels (capillaries) to become so thick and weak that they bleed, leak protein, and slow the flow of blood. Diabetics may develop microangiopathy with thickening of capillaries in many areas including the eyes, feet, legs, and kidneys.
Diabetic neuropathy: Diabetic neuropathy, or nerve damage, occurs due to excess blood sugar levels that can injure the walls of the tiny blood vessels (capillaries) that nourish the nerves, especially in the legs. Diabetic neuropathy can cause tingling, numbness, burning, or pain that usually begins at the tips of the toes or fingers and over a period of months or years gradually spreads upward. Left untreated, the individual can lose all sense of feeling in the affected limbs. Diabetic neuropathy is a common cause of limb amputations. The injuries to the skin occur and are not felt, due to neuropathy, until infection progresses too far to save the tissue, especially the toes and feet. Damage to the nerves that control digestion can cause problems with nausea, vomiting, diarrhea, or constipation. For men, erectile dysfunction may also occur as a result of poor blood flow to the penis and nerve damage, both caused by diabetes.
Diabetic nephropathy: Diabetic nephropathy causes kidney damage and is a complication of diabetes that is caused by uncontrolled high blood sugar. High blood sugar damages the filtering system of the kidneys. Over time, the damage can lead to kidney failure. Diabetic nephropathy is the most common cause of kidney failure in the United States. Severe damage can lead to kidney failure or irreversible end-stage kidney disease, requiring dialysis or a kidney transplant.
Eye damage: Chronic high blood sugars levels damage sensitive blood vessels in the eye, resulting in blurry vision and vision damage. Diabetes can damage the blood vessels of the retina (diabetic retinopathy), potentially leading to blindness. The primary cause of legal blindness in the working population of the United States today is diabetes mellitus. Diabetes also increases the risk of other serious vision conditions, such as cataracts and glaucoma.
Foot ulcers: Nerve damage in the feet or poor blood flow to the feet increases the risk of various foot complications, including diabetic foot ulcers. Left untreated, cuts and blisters can become serious infections. Severe damage might require toe, foot, or even leg amputation.
Skin and mouth conditions: Diabetes may leave the individual more susceptible to skin problems, including bacterial infections, fungal infections, and itching. Gum infections also may be a concern, especially if there is a history of poor dental hygiene.
Osteoporosis: Diabetes may lead to lower than normal bone mineral density, increasing the risk of osteoporosis. Osteoporosis is a disease in which bones become fragile and more likely to break. If not prevented or if left untreated, osteoporosis can progress painlessly until a bone breaks.
Type 2 diabetes may increase the risk of Alzheimer's disease (AD). Alzheimer's disease is a progressive degenerative disease of the nervous system that leads to dementia and eventually death. The more uncontrolled blood sugar levels are, the greater the risk of developing AD. Researchers have found that cardiovascular problems caused by diabetes may contribute to dementia by blocking blood flow to the brain or causing strokes (neurological damage caused by lack of oxygen to the brain). Other possibilities are that too much insulin in the blood leads to brain-damaging inflammation, or lack of insulin in the brain deprives brain cells of glucose.
Gastroparesis: Gastroparesis is a disorder that affects people with both type 1 and type 2 diabetes. In gastroparesis, movement of food through the stomach slows or stops completely. The muscles in the wall of the stomach work poorly or not at all, preventing the stomach from emptying properly. This can interfere with digestion and cause nausea and vomiting, problems with blood sugar control, and malnutrition.
Depression: Studies report that individuals with diabetes have a greater risk of depression than individuals without diabetes. Causes underlying the association between depression and diabetes are unclear. Depression may develop because of stress but also may result from the metabolic effects of diabetes on the brain. Studies suggest that people with diabetes who have a history of depression are more likely to develop diabetic complications than those without depression.
Family history: Having a family history of the disease increases the chance that an individual will develop antibodies to the insulin-making cells (beta cells) in the pancreas. But being genetically predisposed to type 1 diabetes does not mean that the individual will develop diabetes. Only about 10-15% of individuals with type 1 diabetes have a family history of the disease. If the father has the disease, a child has a 6% risk of developing it. If a sibling has the disease, a child has a 5% risk of developing it. If the mother has the disease, a child has a 2% risk of developing it. If an identical twin has the disease, the other twin has a 30% to 50% risk of developing it. If both a parent and one sibling have the disease, a child has a 30% risk of developing it.
Ethnicity: Caucasian individuals have an increased risk for developing type 1 diabetes compared to African-Americans, Asians, or Latinos.
Presence of islet cell antibodies in the blood: People who have both a family history of type 1 diabetes and islet cell antibodies in their blood are likely to develop the disease.
Viral infections during childhood: A child who has certain viral infections, particularly Coxsackie B infections, has a risk almost six times greater of developing type 1 diabetes than children who have not had this type of viral infection. However, this does not mean that the child will definitely develop type 1 diabetes. It is unclear how these infections lead to type 1 diabetes.
Lack of breastfeeding: Children who have a genetic tendency for type 1 diabetes and stop breastfeeding before three months of age or who are given cow's milk formula before four months of age, have a slightly increased risk for developing type 1 diabetes. Children who have a sibling with diabetes and drink more than two, eight ounce glasses of cow's milk per day during childhood may have a four times greater risk of developing antibodies for type 1 diabetes, increasing the risk of developing the disease. Doctors are uncertain how cow's milk actually plays a role in the development of type 1 diabetes. Insulin in the cow's milk may be a factor.
Type 2 diabetes
Age: The risk of developing type 2 diabetes begins to rise significantly at about age 45, and rises considerably after age 65 years. This may be due to a decrease in exercise, loss of muscle mass, and increased weight. However, type 2 diabetes is increasing dramatically among children, adolescents, and younger adults.
Family history: The risk of type 2 diabetes increases if a parent or sibling has type 2 diabetes.
Pregnancy: Developing gestational diabetes increases the risk of developing type 2 diabetes later in life. Also, giving birth to a baby weighing more than nine pounds increases the risk of developing type 2 diabetes. About 3-8% of pregnant women in the United States develop gestational diabetes.
Inactivity: The less active an individual is, the greater the risk of developing type 2 diabetes. Physical activity helps control weight, uses glucose as energy, and makes cells more sensitive to insulin.
Pre-diabetes: Pre-diabetes is a condition in which the blood sugar level is higher than normal, but not high enough to be classified as type 2 diabetes. Left untreated, pre-diabetes often progresses to type 2 diabetes. Recent research has shown that some long-term damage to the body, especially the heart and circulatory system, may already be occurring during pre-diabetes. There are 54 million people in the United States who have pre-diabetes.
Ethnicity: Certain ethnic groups, such as African Americans, Native Americans, Latinos, and Japanese Americans, have a greater risk of developing type 2 diabetes than Caucasians.
Being overweight is a primary risk factor for type 2 diabetes. The more fatty tissue, the more resistant cells become to insulin. Fat cells actually produce hormones, such as leptin and adiponectin, which decrease insulin tissue sensitivity, potentially leading to diabetes mellitus type 2.
Metabolic syndrome: Metabolic syndrome, including high blood pressure, high cholesterol levels, and abdominal obesity, increases the chances of developing type 2 diabetes.
Maturity-onset diabetes of the young (MODY)
Patients at risk for maturity-onset diabetes of the young (MODY) have a strong family history of diabetes, and/or have developed diabetes before middle age. There is a 50% chance for a child to inherit MODY if either parent has MODY. In the field of genetics, this is called autosomal dominant inheritance. MODY is also referred to as a monogenic form of diabetes, which describes its ability to be inherited by a single pair of genes.