There are two types of hypertension.

Primary (or necessary) hypertension

The majority of adults have no identifiable cause of high blood pressure. This type of high blood pressure, known as primary (essential) hypertension, develops gradually over time.

Secondary hypertension:

Some people have high blood pressure as a result of a medical condition. Secondary hypertension is a type of high blood pressure that appears suddenly and causes higher blood pressure than primary hypertension. Secondary hypertension can be caused by a variety of conditions and medications, including:

• Obstructive sleep apnea
• Kidney infection
• Adrenal gland tumours
• Thyroid crises
• Certain defects you’re born with (congenital) in blood vessels
• Certain medications, such as birth control pills, cold remedies, decongestants, over-the-counter pain relievers and some prescription drugs.
• Illegal drugs, such as cocaine and etc.

High blood pressure has many risk factors, including:

1. Age. 
The risk of high blood pressure increases as you age. Until about age 64, high blood pressure is more common in men. Women are more likely to develop high blood pressure after age 65.

2. Race. 
High blood pressure is particularly common among people of African heritage, often developing at an earlier age than it does in whites. Serious complications, such as stroke, heart attack and kidney failure, also are more common in people of African heritage.

3. Family history. 
High blood pressure tends to run in families.

4. Being overweight or obese. 
The more you weigh, the more blood you need to supply oxygen and nutrients to your tissues. As the amount of blood flow through your blood vessels increases, so does the pressure on your artery walls.

5. Not being physically active. 
Inactive people tend to have higher heart rates. The higher your heart rate, the harder your heart must work with each contraction and the stronger the force on your arteries. Lack of physical activity also increases the risk of being overweight.

6. Using tobacco. 
Not only does smoking or chewing tobacco immediately raise your blood pressure temporarily, but the chemicals in tobacco can damage the lining of your artery walls. This can cause your arteries to narrow and increase your risk of heart disease. Secondhand smoke also can increase your heart disease risk.

7. Too much salt (sodium) in your diet. 
Too much sodium in your diet can cause your body to retain fluid, which increases blood pressure.

8. Too little potassium in your diet. 
Potassium helps balance the amount of sodium in your cells. A proper balance of potassium is critical for good heart health. If you don’t get enough potassium in your diet, or you lose too much potassium due to dehydration or other health conditions, sodium can build up in your blood.

9. Drinking too much alcohol. 
Over time, heavy drinking can damage your heart. Having more than one drink a day for women and more than two drinks a day for men may affect your blood pressure.
If you drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women and two drinks a day for men. One drink equals 12 ounces of beer, 5 ounces of wine or 1.5 ounces of 80-proof liquor.

10. Stress.
High levels of stress can lead to a temporary increase in blood pressure. Stress-related habits such as eating more, using tobacco or drinking alcohol can lead to further increases in blood pressure.

11. Certain chronic conditions.
Certain chronic conditions also may increase your risk of high blood pressure, including kidney disease, diabetes and sleep apnea.

• Sometimes pregnancy contributes to high blood pressure as well.