Patient information: Preventing complications in diabetes mellitus (Beyond the Basics)
- David K McCulloch, MD
David K McCulloch, MD
- Clinical Professor of Medicine
- University of Washington
Diabetes mellitus is a chronic condition that can lead to complications over time. These complications can include:
●Coronary heart disease, which can lead to a heart attack
●Cerebrovascular disease, which can lead to stroke
●Retinopathy (disease of the eye), which can lead to blindness
●Nephropathy (disease of the kidney), which can lead to kidney failure and the need for dialysis
●Neuropathy (disease of the nerves), which can lead to, among other things, ulceration of the foot requiring amputation (see "Patient information: Diabetic neuropathy (Beyond the Basics)")
Many of these complications produce no symptoms in the early stages, and most can be prevented or minimized with a combination of regular medical care and blood sugar monitoring.
CARDIOVASCULAR COMPLICATIONS IN DIABETES
A number of measures are important to reduce the risk of cardiovascular (heart and blood vessel) disease.
●Manage high blood pressure with lifestyle modifications and/or medication(s).
●Have a blood test to measure cholesterol and triglyceride levels, and modify the diets if needed. Some people will also need a medication to lower their low-density lipoprotein (LDL) (“bad cholesterol”) or triglycerides.
If medication is needed, a statin drug should be included whenever possible. The statin drugs have been shown to decrease the future risk of heart attacks, strokes, and death in people with diabetes who are over age 40 years, even when cholesterol levels are normal.
The initiation of statins should be based upon cardiovascular risk rather than an LDL cholesterol level. Statins are recommended for anyone with clinical cardiovascular disease or over age 40 years, regardless of baseline lipid levels. For patients without clinical cardiovascular disease and under age 40 years, statins can be added (in addition to lifestyle intervention) if there are multiple cardiovascular disease risk factors. The intensity of statin therapy can be adjusted based upon side effects, tolerability, and LDL cholesterol levels. The American Diabetes Association (ADA) recommends that people with diabetes have an LDL cholesterol level less than 100 mg/dL (2.59 mmol/L). Some studies suggest lowering LDL even further, to 70 to 80 mg/dL (1.81 to 2.07 mmol/L). (See "Patient information: High cholesterol and lipids (hyperlipidemia) (Beyond the Basics)".)
●Aspirin (81 to 100 mg per day) is recommended for anyone with diabetes who already has or is at increased risk of cardiovascular disease.
CONTROLLING BLOOD SUGAR IN DIABETES
The long-term complications of diabetes are caused by the effect of high blood sugar levels on blood vessels. Two important studies, the Diabetes Control and Complications Trial (DCCT) in patients with type 1 diabetes and the United Kingdom Prospective Diabetes Study (UKPDS) in patients with type 2 diabetes, found that people with lower blood sugar levels had fewer complications than those with higher values.
Thus, keeping blood sugars close to normal can help prevent the long-term complications of diabetes mellitus. However, there are some risks associated with tight control, particularly an increased risk of hypoglycemia (low blood sugar).
Monitoring blood sugar levels — Monitoring blood sugar with finger sticks at home can indicate how well diabetes is controlled and serves as a guide to adjusting therapy (see "Patient information: Self-blood glucose monitoring in diabetes mellitus (Beyond the Basics)"). For most people, a target for fasting blood sugar and for blood sugar levels before each meal is 80 to120 mg/dL (4.4 to 6.6 mmol/L); however, these targets may need to be individualized.
A blood test called A1C (glycated hemoglobin) is also used to monitor blood sugar control; the result provides an average of blood sugar levels during the previous one to three months. An A1C of 7 percent or less is recommended; this corresponds to an average blood sugar of 150 mg/dL (8.3 mmol/L) (table 1).
The A1C target may be somewhat higher in people who are older or who have conditions that increase the risks associated with hypoglycemia. Even small decreases in the A1C lower the risk of diabetes-related complications to some degree.
The combination of A1C and fingerstick blood sugars provides information about the average and daily blood sugar levels.
Type 1 diabetes — Blood sugar control in type 1 diabetes requires some form of insulin, which can be given with insulin injections or an insulin pump. Most healthcare providers recommend intensive insulin therapy, which requires frequent blood sugar monitoring in addition to frequent injections or use of an insulin pump. (See "Patient information: Diabetes mellitus type 1: Insulin treatment (Beyond the Basics)".)
Intensive insulin therapy increases the risk of low blood sugar, is more expensive than traditional insulin therapy, and requires that the person monitor their blood sugar levels, diet, and activities. Some people who use intensive insulin therapy gain weight, although regular exercise and controlling the amount eaten can prevent weight gain. (See "Patient information: Hypoglycemia (low blood sugar) in diabetes mellitus (Beyond the Basics)".)
Type 2 diabetes — With type 2 diabetes, it is sometimes possible to control blood sugar levels with lifestyle changes, often in combination with oral medications. Insulin injections may be needed when a person is first diagnosed or later in the course of treatment. Most people with type 2 diabetes who take insulin require only one or two injections per day. In 2015, an inhaled form of insulin became available for clinical use. Inhaled insulins have not been shown to be effective in reducing A1C levels to the goal of less than 7 percent that is often recommended. (See "Patient information: Diabetes mellitus type 2: Insulin treatment (Beyond the Basics)".)
EYE COMPLICATIONS IN DIABETES
Regular eye examinations are essential for detecting eye complications (called retinopathy) at an early stage, when the condition can be monitored and treated to preserve vision.
An eye exam should include dilating the pupils (with medicated eye drops) to completely examine the retina. Unless the pupils are medicated, they contract in response to light, making it impossible to view the entire retina. In some people with retinopathy, photographs of the retina will be taken to monitor the changes. This examination should be performed by a doctor who specializes in the eyes (called an ophthalmologist or optometrist).
The risk of diabetic retinopathy varies with the type and duration of diabetes and with other life events. Thus, the screening guidelines differ from one person to another.
Type 1 diabetes — People with type 1 diabetes should have an eye examination by an ophthalmologist or optometrist beginning five years after they are diagnosed with diabetes, although screening is usually not necessary before puberty. People who have difficulty with their vision or who require glasses or contacts may need to be seen sooner. The frequency of subsequent examinations will depend upon the results of the initial exam. An eye exam is usually recommended every one to two years after the initial examination.
Type 2 diabetes — People with type 2 diabetes should have an eye examination by an ophthalmologist or optometrist when they are first diagnosed with diabetes. The reason for this is that blood sugar levels often increase over a period of several years before the person is diagnosed. Eye complications can develop during this time and often have no symptoms. Having an eye examination soon after diagnosis can help to determine if there are eye complications, the extent or severity of the complications, and if treatment is needed.
The frequency of subsequent exams will depend upon the results of the initial examination. An eye exam is usually recommended every one to two years after the initial examination.
FOOT CARE WITH DIABETES
Diabetes can decrease the blood supply to the feet and damage the nerves that carry sensation. These changes put the feet at risk for developing potentially serious complications such as ulcers. Foot complications are very common among people with diabetes, and may go unnoticed until the condition is severe. (See "Patient information: Diabetic neuropathy (Beyond the Basics)".)
Self exam — People with diabetes should examine their feet every day. It is important to examine all parts of the feet, especially the area between the toes. Look for broken skin, ulcers, blisters, areas of increased warmth or redness, or changes in callus formation; a healthcare provider should be notified if any of these changes are found. (See "Patient information: Foot care in diabetes mellitus (Beyond the Basics)".)
This examination can be a part of the daily bathing or dressing routine. It may be necessary to use a mirror to see the bottoms of the feet clearly. Anyone who is unable to reach their feet or see them completely, even with the help of a mirror, should have someone else (such as a spouse or other family member) assist with the examination.
Clinical exam — During a routine medical visit, the clinician will check the blood flow and sensation in the feet. In people with type 1 diabetes, annual foot examinations should begin five years after diagnosis. In people with type 2 diabetes, annual foot exams should begin at the time of diagnosis.
During a foot examination, the clinician will look for changes such as ulcers, cold feet, thin skin, bluish skin color, and skin breaks associated with athlete's foot. The clinician will also test the sensation in the feet to determine if it is normal or diminished. People with decreased sensation are at risk for foot injuries that can go unnoticed due to lack of pain.
KIDNEY COMPLICATIONS IN DIABETES
Diabetes can alter the normal function of the kidneys. A urine test that measures the amount of protein (albumin) in the urine can determine if diabetes is affecting the kidney's filtering action. Microscopic amounts of albumin in the urine (microalbuminuria) can be an early indicator of diabetes-related kidney complications (called nephropathy). The amount of albumin in the urine can also help the provider determine if nephropathy is worsening. (See "Patient information: Protein in the urine (proteinuria) (Beyond the Basics)".)
Urine screening tests should begin in people with type 1 diabetes about five years after diagnosis, and in people with type 2 diabetes at the time of diagnosis. If the test shows that there is protein in the urine, tight blood sugar and lipid (cholesterol and triglyceride) control are recommended.
A blood pressure medication (an angiotensin-converting enzyme [ACE] inhibitor or angiotensin receptor blocker [ARB]) is generally recommended if albuminuria does not improve, even if the blood pressure is normal. People with elevated blood pressure and albuminuria are also treated with an ACE inhibitor or ARB. These medications decrease the amount of protein in the urine and can prevent or slow the progression of diabetes-related kidney disease.
HYPERTENSION AND RELATED COMPLICATIONS IN DIABETES
Many people with diabetes have hypertension (high blood pressure). Although high blood pressure causes few symptoms, it has two negative effects: it stresses the cardiovascular system and speeds the development of diabetic complications of the kidney and eye. A healthcare provider can diagnose high blood pressure by measuring blood pressure on a regular basis. (See "Patient information: High blood pressure in adults (Beyond the Basics)".)
A blood pressure reading below 140/90 and perhaps below 130/80 is recommended for most people with diabetes who do not have kidney complications; a lower blood pressure goal (less than 130/80) is recommended for people with diabetes who have kidney disease.
If a person is diagnosed with prehypertension (>120/80), the healthcare provider may recommend weight loss, exercise, decreasing the amount of salt in the diet, quitting smoking, and decreasing alcohol intake. These measures can sometimes reduce blood pressure to normal. (See "Patient information: High blood pressure, diet, and weight (Beyond the Basics)".)
If these measures are not effective or the blood pressure must be lowered quickly, the provider will likely recommend one of several high blood pressure medications. The provider can discuss the pros and cons of each medication and the goals of treatment. (See "Patient information: High blood pressure treatment in adults (Beyond the Basics)".)
PREGNANCY AND DIABETES
Control of diabetes and its potential complications is especially important for women who are planning to become pregnant, as well as in those who already are pregnant. Controlling blood sugar levels before and during pregnancy decreases the risk of many complications in both the mother and the baby. A separate topic review is available on this subject. (See "Patient information: Care during pregnancy for women with type 1 or 2 diabetes mellitus (Beyond the Basics)".)
WHERE TO GET MORE INFORMATION
Your healthcare provider is the best source of information for questions and concerns related to your medical problem.
This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.
Patient level information — UpToDate offers two types of patient education materials.
The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.
Patient information: Type 2 diabetes (The Basics)
Patient information: The ABCs of diabetes (The Basics)
Patient information: Recovery after coronary artery bypass graft surgery (CABG) (The Basics)
Patient information: Diabetic ketoacidosis (The Basics)
Patient information: Hyperosmolar nonketotic coma (The Basics)
Patient information: Gangrene (The Basics)
Patient information: Detached retina (The Basics)
Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.
Patient information: Care during pregnancy for women with type 1 or 2 diabetes mellitus (Beyond the Basics)
Patient information: Foot care in diabetes mellitus (Beyond the Basics)
Patient information: High blood pressure in adults (Beyond the Basics)
Patient information: High cholesterol and lipids (hyperlipidemia) (Beyond the Basics)
Patient information: High cholesterol treatment options (Beyond the Basics)
Patient information: Self-blood glucose monitoring in diabetes mellitus (Beyond the Basics)
Patient information: Diabetic neuropathy (Beyond the Basics)
Patient information: Diabetes mellitus type 1: Insulin treatment (Beyond the Basics)
Patient information: Hypoglycemia (low blood sugar) in diabetes mellitus (Beyond the Basics)
Patient information: Diabetes mellitus type 2: Insulin treatment (Beyond the Basics)
Patient information: Protein in the urine (proteinuria) (Beyond the Basics)
Patient information: High blood pressure, diet, and weight (Beyond the Basics)
Patient information: High blood pressure treatment in adults (Beyond the Basics)
Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.
Clinical presentation and diagnosis of diabetes mellitus in adults
Estimation of blood glucose control in diabetes mellitus
Glycemic control and vascular complications in type 1 diabetes mellitus
Glycemic control and vascular complications in type 2 diabetes mellitus
Pregestational diabetes mellitus: Glycemic control during pregnancy
Management of blood glucose in adults with type 1 diabetes mellitus
Insulin therapy in type 2 diabetes mellitus
Management of diabetes mellitus in hospitalized patients
Management of persistent hyperglycemia in type 2 diabetes mellitus
Overview of medical care in adults with diabetes mellitus
Screening for type 2 diabetes mellitus
Treatment of hypertension in patients with diabetes mellitus
Treatment of type 2 diabetes mellitus in the older patient
The following organizations also provide reliable health information.
●National Library of Medicine
●National Institute of Diabetes and Digestive and Kidney Diseases
●American Diabetes Association (ADA)
●Hormone Health Network
(www.hormone.org, available in English and Spanish)
- The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. The Diabetes Control and Complications Trial Research Group. N Engl J Med 1993; 329:977.
- Effect of intensive diabetes management on macrovascular events and risk factors in the Diabetes Control and Complications Trial. Am J Cardiol 1995; 75:894.
- Abraira C, Colwell JA, Nuttall FQ, et al. Veterans Affairs Cooperative Study on glycemic control and complications in type II diabetes (VA CSDM). Results of the feasibility trial. Veterans Affairs Cooperative Study in Type II Diabetes. Diabetes Care 1995; 18:1113.
- Nathan DM, Cleary PA, Backlund JY, et al. Intensive diabetes treatment and cardiovascular disease in patients with type 1 diabetes. N Engl J Med 2005; 353:2643.
- Writing Team for the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Research Group. Sustained effect of intensive treatment of type 1 diabetes mellitus on development and progression of diabetic nephropathy: the Epidemiology of Diabetes Interventions and Complications (EDIC) study. JAMA 2003; 290:2159.
- Gray A, Raikou M, McGuire A, et al. Cost effectiveness of an intensive blood glucose control policy in patients with type 2 diabetes: economic analysis alongside randomised controlled trial (UKPDS 41). United Kingdom Prospective Diabetes Study Group. BMJ 2000; 320:1373.
All topics are updated as new information becomes available. Our peer review process typically takes one to six weeks depending on the issue.