High blood pressure in one arm

Why is the blood pressure slightly up in my right arm compared to the left arm?

Mild variations in BP are very common between the two arms. Usually the difference is less than 10 mmHg. I would not worry about it. In rare cases, the BP may be elevated in the left arm, and a disorder known aortic coarctation may be responsible. This disorder is usually identified in infancy or childhood. If the blood pressure is significantly low in one arm, it maybe due to a block in the blood vessel which runs underneath the collar bone. In such cases, you may need to see a surgeon- I mean a good surgeon. Most surgeons do not have a clue how to fix this disorder (thoracic outlet syndrome) and I would be very careful when it comes to selecting a surgeon.