Blood Pressure and Diabetes

Blood Pressure and Diabetes


High blood pressure (hypertension) is a sign that the heart and blood vessels are being overworked. The condition is a major factor in the health complications that occur in people with diabetes, and controlling blood pressure is crucial to maintaining good health.

High blood pressure occurs when the force of blood against artery walls becomes excessive. In people with diabetes, high blood pressure increases the risk of serious and life-threatening diseases, including:

  • Vascular damage (diabetic angiopathy and atherosclerosis)
  • Heart attack, other heart conditions and stroke
  • Diabetic nephropathy and chronic kidney failure
  • Eye diseases such as diabetic retinopathy and glaucoma

Most people with diabetes have or will develop high blood pressure. Because diabetes and high blood pressure are so closely linked, the American College of Physicians emphasizes that controlling blood pressure should be as high a priority for people with diabetes as controlling glucose (blood sugar).

In addition, people with diabetes are classified as hypertensive earlier than nondiabetics. Nondiabetics are considered to be hypertensive when their blood pressure measures 140/90 millimeters of mercury (mmHg) or higher. Blood pressure is considered high when either the top number (systolic pressure) or the bottom number (diastolic pressure) is above those levels. People with diabetes are classified as hypertensive when systolic pressure is 130 mmHg or higher, or diastolic pressure is 80 mmHg or higher.

The American Diabetes Association (ADA) and the National Heart, Lung and Blood Institute recommend that patients with diabetes and/or kidney disease receive treatment if their blood pressure is above 130/80 mmHg. These levels are slightly stricter than those recommended for the general population.

The ADA recommends that people with diabetes have their blood pressure checked during every visit to a physician, or at least two to four times each year.

Most cases of high blood pressure have no cure, but the overwhelming majority can be managed with diet and medication. In general, for every 10 mmHg reduction in systolic blood pressure, the risk for any diabetic complication is reduced by 12 percent, according to the U.S. Centers for Disease Control and Prevention.

Although diabetes is strongly associated with high blood pressure, diabetic individuals can also experience potentially dangerous low blood pressure (hypotension). Several factors linked to this condition can be addressed to reduce the risk of dizziness and fainting.

About blood pressure and diabetes

High blood pressure (hypertension) is a dangerous elevation of the force pushing against the artery walls. It is common in people with diabetes.

Between 60 and 65 percent of people with diabetes have high blood pressure, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). The National Diabetes Education Program raises that estimate to 70 percent. African Americans, American Indians and Alaska Natives are particularly at risk.

Blood pressure is the measure of the force of the blood pushing against the walls of the arteries, the blood vessels that carry blood from the heart to the rest of the body. When the heart contracts to pump out blood, the peak of contraction is called systolic pressure. After pumping, the heart relaxes and pressure drops to its lowest point just before a new beat. That lowest point is called the diastolic pressure.

The measurement of blood pressure is expressed as systolic pressure over diastolic pressure. For example, normal blood pressure for adults is considered to be in the range of 120/80 millimeters of mercury (mmHg). Patients with diabetes and/or kidney disease require treatment if their blood pressure is above 130/80 mmHg. This standard is stricter than it is for nondiabetic adults. Generally, blood pressure 140/90 mmHg and above is considered high for nondiabetic adults.

The combination of high blood pressure and diabetes can have dangerous consequences, because both conditions can damage the lining of the arteries. The high glucose (blood sugar) levels associated with diabetes frequently damage the major arteries that supply oxygen-rich blood to the heart, brain and other major organs. Fatty deposits called plaques build up (atherosclerosis) and create blockages that hinder blood flow.

When the arteries that supply the heart muscle become narrowed by plaques, it is known as coronary artery disease (also called coronary heart disease). This in turn contributes to high blood pressure, a leading source of cardiovascular problems.

Diabetic neuropathy can also contribute to high blood pressure by damaging the nerves that regulate blood pressure (autonomic neuropathy).

High blood pressure can:

  • Accelerate the damage to arteries, causing them to further harden, thicken and narrow.
  • Cause blood vessels to expand and bulge (aneurysm).
  • Trigger blockage or rupture of blood vessels leading to the brain, causing a stroke.
  • Abnormally thicken the heart muscle, causing heart disease.
  • Damage or accelerate damage to the kidneys (known as diabetic nephropathy), which can lead to chronic kidney failure.
  • Increase or accelerate microvascular damage to blood vessels in the eyes, raising the risk of diabetic retinopathy and blindness.
  • Increase the risk and worsen the damage of glaucoma.
  • Increase the risk of developing cataracts and macular degeneration.

Cardiovascular disease is the leading cause of death in people with diabetes, who are two to four times more likely to have heart disease or stroke. In general, for every 10 mmHg reduction in systolic blood pressure, the risk for any diabetic complication is reduced by 12 percent, according to the U.S. Centers for Disease Control and Prevention.

The risk of developing one or more serious health conditions increases as blood pressure rises. High blood pressure has often been called the “silent killer” because mild to moderate levels usually go unnoticed by patients until serious damage has already been done.

High blood pressure is also a component of metabolic syndrome, a cluster of conditions that increase a person’s risk of developing type 2 diabetes and cardiovascular disease.

Data from the National Health and Nutrition Examination Survey revealed in 2006 that Americans’ control of high blood pressure has improved in recent years. However, the American Diabetes Association (ADA) notes that far too few people with diabetes adequately treat their blood pressure conditions. The ADA has also found that many physicians are not as vigilant as they should be in controlling blood pressure in their patients with diabetes.

Although diabetes is strongly associated with high blood pressure, people with diabetes, even those who are usually hypertensive, can experience low blood pressure (hypotension). This low blood pressure most often may be seen when an individual goes from lying down to sitting or standing, or from sitting to standing (postural or orthostatic hypotension). 

Postural hypotension may be defined as a decline in systolic blood pressure of 20 mmHg or more when a person stands up. This condition often causes dizziness and may cause fainting.

Factors that can increase the risk of diabetic hypotension include:

  • Certain drugs, including antihypertensives and some heart, antiseizure, psychiatric and opioid medications
  • Diabetic neuropathy
  • Dehydration
  • Poor glucose control
  • Kidney dialysis
  • Anemia (insufficient red blood cells)
  • Advanced age

In addition to diabetes, some other endocrine conditions can also involve low blood pressure, including hypothyroidism, hyperthyroidism and Addison’s disease (adrenal insufficiency).

People with diabetes can reduce their chances of hypotension by following their physician’s treatment plan, taking medications as directed, informing their physician of drug side effects, controlling glucose and moving from sitting to standing slowly and carefully.

Risk factors and potential causes

Several factors contribute to high blood pressure in people with diabetes. They include:

  • Obesity. About 80 percent of patients with type 2 diabetes are also obese.
  • Atherosclerosis. A buildup of fatty deposits on the inner walls of arteries. Unhealthy levels of cholesterol contribute to atherosclerosis.
  • Kidney disease. High blood pressure can damage the blood vessels throughout the body. This can cause water retention within the blood vessels in the kidneys. In turn, blood pressure rises even more, causing more damage.
  • Race and ethnicity. Black Americans, who have above-average rates of type 2 diabetes, are prone to high blood pressure and tend to develop it a younger age than people of other races.
  • Genetics and family history. Researchers have identified dozens of genes that contribute to high blood pressure. The condition may run in families.
  • Age and sex. The risk of high blood pressure increases as people get older. Men are more likely than women to suffer high blood pressure before age 55, but by age 74 women have higher rates of this condition.

Other contributors to high blood pressure include chronic stress, lack of exercise, smoking, excess use of alcohol, a diet high in salt or insufficient in potassium, sleep apnea, and certain medications, possibly including the popular painkillers aspirin, ibuprofen and acetaminophen.

Diagnosis methods for diabetic hypertension

When diagnosing high blood pressure (hypertension), a physician will obtain a patient’s medical history. For example, the physician will ask whether high blood pressure runs in the family and what the patient’s dietary habits have been like (e.g., salt intake). A physician is also likely to perform a cholesterol test and glucose test, and to inquire about the patient’s level of activity.

The physician will perform a physical examination, which may include checking the patient’s blood pressure in both arms while standing and lying down. The American Diabetes Association recommends that people with diabetes have their blood pressure checked during every visit to a physician, or at least two to four times each year.

In some cases, the physician may ask patients to take their own blood pressure at home and bring in a daily log of blood pressure measurements. This strategy will help establish an individual’s normal blood pressure pattern and rule out “white coat hypertension” (blood pressure that is high only during a medical checkup, because of anxiety or stress). Another option may be ambulatory blood pressure monitoring, in which a patient wears a device that automatically assesses blood pressure, typically for 24 hours.

Blood pressure is measured by wrapping an arm cuff (attached to a monitor called a sphygmomanometer) snugly around the patient’s arm and then using a stethoscope to listen to the brachial artery located at the inside elbow on the same arm. The cuff is then pumped full of air until circulation is briefly cut off. Then some air will be slowly let out of the device, loosening the cuff’s grip on the arm and releasing the blood to flow freely again.

As the air is let out, the examiner watches the numbers coming down on a sphygmomanometer and waits until first hearing the heartbeat. The number at which that occurs is the systolic pressure. The examiner remembers this as the numbers continue to come down on the monitor and notes the number at which the heartbeat is last heard. The number at which that occurs is the diastolic pressure. Other blood pressure measurement devices may also be used. Some use mercury manometers to measure the pressure, and others employ digital readouts.

Reliable blood pressure monitors are available if people are interested in monitoring their own blood pressure or that of their family members. When buying these monitors, it is important to consult with a physician or a consumer product rating agency regarding the reliability of home monitors.

Generally, arm cuff digital monitors are the easiest and most reliable to use but should be periodically checked against a mercury sphygmomanometer. Researchers are also testing 24-hour blood pressure monitors, with early studies focusing on patients with high blood pressure who are at increased risk for a heart attack.

After the physical exam, a number of tests will often be ordered, which may include:

  • Urinalysis and blood tests such as an electrolyte panel and waste product tests to rule out kidney diseases such as diabetic nephropathy.
  • Electrocardiogram (EKG or ECG), which measures the heart’s electrical activity. By analyzing the results, a physician can check for heart problems that could be associated with high blood pressure, such as heart failure or left ventricular hypertrophy.
  • Echocardiogram, which uses ultrasound waves to visualize the structures and functions of the heart. This test is also used to check for heart problems such as left ventricular hypertrophy.
  • Chest x-ray to rule out an enlarged heart.

For patients who experience dizziness or fainting that may be due to sudden drops in blood pressure, which can result from dehydration or stress, a physician may recommend a tilt-table test. This test is conducted with the patient secured to a platform that pivots up and down.

Once a diagnosis has been made and serious problems such as kidney disease have been ruled out, then treatment can begin. However, very high or low blood pressure may require additional testing to rule out an unusual cause.

Treatment and prevention

Controlling blood pressure is one of the ABCs of diabetes treatment, according to the American College of Physicians, which include:

  • A – Glucose control
  • B – Blood pressure control
  • C – Cholesterol control

A healthy blood pressure reading is one of the most important factors in preserving kidney function and reducing the risk of cardiovascular disease. People with diabetes diagnosed with high blood pressure can help keep their disorder under control by scheduling the following tests with their healthcare provider:

  • Every three to four months
    • Glycohemoglobin test. This blood test measures the average amount of glucose in blood over the past few months.
    • Blood pressure check.
    • Weight check.
  • Each year
    • Cholesterol test. This testing includes total cholesterol, LDL (“bad”) cholesterol, VLDL (“very bad”) cholesterol, HDL (“good”) cholesterol and triglycerides.
    • Microalbuminuria test. A urine test that can detect early kidney disease.

Lifestyle changes can significantly improve a patient’s blood pressure. Steps that can and should be taken to lower and control blood pressure include:

  • Quitting smoking. This is perhaps the most important action a smoker can take to promote good health. Among its many other health hazards, smoking elevates blood pressure.
  • Proper diet. A registered dietitian can assist in nutritional counseling to help control glucose (blood sugar) and maximize cardiovascular health. Recommended diets typically are rich in high-fiber plant foods, allow adequate lean protein and “good” fats (e.g., olive oil, nuts), limit sodium, sugars, starches and saturated fats, and avoid trans fats.
  • Improving levels of cholesterol. Unhealthy types of cholesterol play a major role in creating the fatty deposits that can narrow arteries and cause blood pressure to rise. In addition, diabetes tends to increase the damage caused by cholesterol and other lipids, such as triglycerides, and to make it occur more quickly.  The physician may prescribe cholesterol drugs if necessary.
  • Weight loss. Loss of weight in the abdominal area (central obesity) can immediately reduce blood pressure and helps to reduce the size of the heart. Weight loss accompanied by salt restriction may allow people with mild hypertension to reduce or eliminate their need for medication, under their physician’s guidance.
  • Regular aerobic exercise. Patients should generally get 30 to 45 minutes of physical activity each day if possible. Activity at least three to four times a week is helpful for regulating high blood pressure. Regularity of the exercise is more important than the intensity of the workout. Individuals should consult with their physician before starting an exercise program.
  • Limiting consumption of alcohol, such as a maximum of one drink a day for women and two drinks a day for men, if approved by a physician. One drink is defined as one 5-ounce glass (148 milliliters [ml]) of wine a day, one 12-ounce (355 ml) beer or one 1.5-ounce serving (44 ml) of 80-proof distilled spirits. Physicians advise some patients, such as those who are prone to hypoglycemia or have hypoglycemia unawareness, to avoid alcohol.
  • Limiting sodium intake to 2,400 milligrams (2.4 grams) and salt (sodium chloride) intake to 6,000 milligrams (6 grams) a day, according to guidelines of the American Diabetes Association. One teaspoonful of table salt contains 2 grams of sodium and 5 grams of salt.
  • Taking medications as prescribed.
  • Limiting consumption of caffeine.
  • Stress management. Emotional as well as physical factors may play important roles in the development of hypertension.

In addition to these lifestyle changes, patients are often prescribed medications to reduce blood pressure (antihypertensives). In many cases, more than one drug is required to bring high blood pressure under control. Because of the potential for side effects, patients should carefully discuss options with their physician. Blood pressure medications include:

  • ACE inhibitors. These medications are among the most frequently prescribed blood pressure drugs for people with diabetes. ACE inhibitors are vasodilators that help reduce blood pressure by inhibiting the substances in the blood that cause blood vessels to constrict. Recent studies suggest that this class of drugs may be superior to others in preventing stroke, heart disease and kidney disease in patients (especially those with diabetes) with risk factors for vascular disease, and may even benefit people with type 2 diabetes who have normal blood pressure. They are also useful in patients with heart disease. Many physicians prescribe ACE inhibitors to diabetic patients as the primary blood pressure drug but add additional drugs to increase effectiveness.
  • Angiotensin-II receptor blockers (ARBs). Like ACE inhibitors, these drugs have been shown to protect patients from kidney damage in addition to lowering blood pressure.
  • Calcium channel blockers. These vasodilators inhibit the flow of calcium into heart and blood vessel tissues, which reduces tension in the heart, relaxes blood vessels and lowers blood pressure. They are commonly prescribed for those with diabetes and are particularly effective when used in combination with ACE inhibitors or angiotensin-II receptor blockers.
  • Diuretics. Medications that promote the formation of urine in the kidneys, causing the body to flush out excess fluids and minerals, especially sodium. These are often the first medications given to reduce high blood pressure in nondiabetics, are frequently prescribed for people with diabetes as well and may help prevent kidney damage. Though commonly used, they may have unwanted side effects, such as low potassium levels (hypokalemia). Some studies indicate that diuretics may cause hyperglycemia and be a risk factor for diabetes.
  • Alphablockers and beta blockers. Medications that inhibit alpha and beta receptors in the nervous system. This relaxes arteries, decreases the force of the heartbeat and reduces blood pressure. Beta blockers are especially useful in patients with heart disease. However, they can mask symptoms of hyperglycemia, such as increases in pulse rate and blood pressure. For example, the heart rate may not increase as it normally would during episodes of hyperglycemia. Beta blockers may also make hyperglycemia last longer, worsen glucose control and possibly lead to secondary diabetes. 

The majority of patients with high blood pressure will need to take medications for the rest of their lives to control the condition. In some cases, two or three antihypertensives may be given. Recent studies have shown that such a combination of drugs not only lowers blood pressure, but also may reduce the risk of stroke and ischemic heart disease.

Some blood pressure medications can affect a patient’s glucose levels, a particular concern for people with diabetes. Patients should consult with their physician about this potential risk when deciding on medications.

Other research has suggested that some patients with only slightly elevated blood pressures may eventually be able to stop taking medications and control their condition solely through lifestyle changes, such as losing weight and maintaining a low-salt diet. Strategies such as exercise, nutrition plans and, especially, changes in medication should not be undertaken on one’s own, but first discussed with one’s physician.

Researchers have also been exploring the genetic roots of high blood pressure. Identifying genes that cause high blood pressure in a particular patient could help physicians to prescribe the most effective antihypertensive drug.

Treatment options for low blood pressure, which is far less common than high blood pressure, may include drugs that raise blood pressure (antihypotensives), caffeine, increased consumption of salt, or compression stockings worn on the legs.

Questions for your doctor on blood pressure

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about blood pressure and diabetes:

  1. What is my blood pressure? What should it be?
  2. How does diabetes affect my blood pressure, and how does blood pressure affect my diabetes?
  3. How often should I check my blood pressure?
  4. Should I get a home blood pressure kit? If so, which kind?
  5. How often should a doctor review my blood pressure?
  6. Can diet and exercise control my blood pressure?
  7. What kind of diet should I follow? Should I see a registered dietitian?
  8. What kind of exercise should I do? How much and how often?
  9. If I need blood pressure drugs, which kind is best for me?
  10. Can these medications raise my blood sugar or cause other problems?
  11. Can my blood pressure drug also help against kidney disease or other disorders?
  12. Are there symptoms if my blood pressure gets too high?
  13. Is it possible for my blood pressure to be too low?
  14. How can I avoid postural hypotension?
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