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.