Updated November 14, 2014.

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Is your blood pressure high? Do you find that no matter how many medications you are taking or how much you diet and exercise that your blood pressure is very difficult to control? If this is the case, then there are five causes of difficult to control high blood pressure that you and your doctor need to consider. These are causes of high blood pressure of difficult to control high blood pressure that your doctor is likely going to evaluate you for.

1. Sleep Apnea

Do you have problems sleeping? Do you snore so severely that your significant other is up at night? Do you find yourself feeling very tired when you get up in the morning even if you have sleep eight hours? Do you need to take naps during the day or conversely, can you nod off at a moment's notice? If any of the above pertains to you, then you may have sleep apnea. This is one of the most common causes of difficult to control high blood pressure. If you are overweight, this increases your likelihood of developing sleep apnea. The diagnosis of sleep apnea is confirmed by a sleep study called polysomnography and treatment can involve the use of  a CPAP machine.

2. Kidney Disease

Kidney disease is one of the most common causes yet under-appreciated causes of difficult to control high blood pressure. This is a condition that is diagnosed by looking at lab values, especially a creatinine level. While high blood pressure is the second most common cause of kidney disease (behind diabetes), the converse is also true: kidney disease is also a very common cause of difficult to treat high blood pressure.

 

3. Vascular Disease of The Kidney

A cause of difficult to control high blood pressure includes problems with blood flow to the kidney or kidneys. The medical term for this is renal artery stenosis. What are tipoffs that this may be a cause of your high blood pressure? Well, the presence of vascular disease elsewhere as well as the presence of diabetes and high cholesterol are significant risk factors. For example, if you have heart disease, peripheral vascular disease, carotid artery disease or prior history of a stroke, in the presence of diabetes, then this increases the likelihood that you may have a problem with blood flow to your kidneys. There are several ways to diagnose this condition including an ultrasound looking at the blood flow to to your kidneys to a special type of CT scan called a CT angiogram. Many physicians treat this condition conservatively as acute interventions often do not improve the overall condition.

4. Increased Production of  A Hormone Called Aldosterone

Aldosterone is a hormone that is produced by the adrenal gland and plays an important role in the development of difficult to control blood pressure. Important physiologic aspects of this hormone have been discussed in prior blog posts. There are two important aspects here: there is a condition called primary hyperaldosteronism where the adrenal gland is pumping higher doses of aldosterone than normal. This occurs in approximately five percent of the population but i often thought about in cases of difficult to control blood pressure and can be screened for by a simple blood test. More commonly, however, aldosterone is produced by adipose cells (fat cells) and increased production of this hormone can occur when obesity is present. This is one of many reasons why the blood pressure can be elevated in overweight or obese individuals.

5. Others: If the above four conditions have been evaluated for and come back negative, there is a plethora of other condition your doctor will  likely evaluate you for from pheochromocytoma to carcinoid syndrome to many others.