Can a patient of high blood pressure join a gym?

Usually. Regular exercise is a good way to help control high blood pressure. If you've been diagnosed with high blood pressure it's also very important to take your medication. Anyone with uncontrolled high blood pressure should not lift weights. So if you don't know whether your high blood pressure is controlled, see your doctor before joining a gym.
High BP and gym. Regular cardiovascular exercise can lower the blood pressure in the long term. Conversely, weight training can temporarily spike your blood pressure numbers as you're exercising. If your blood pressure is adequately controlled with medication, then both types of exercise would be safe and useful.

Related Questions

Why is exercise not good for the patients high blood pressure?

It is Good! Exercise has many cardiovascular benefits. A regular exercise program has been shown to be part of a successful weight reduction program, improve cardiovascular function and help reduce hypertension and its ill effects. However, since blood pressure normally rises with exercise those with severe hypertension may need a graduated, supervised and monitored program to start. Read more...
It is good. While blood pressure can increase during exercise as the body needs more oxygen delivered to the tissues, regular exercise actually is associated with a decreased risk of hypertension and an improved blood pressure control. One should start an exercise program slowly and build up over time. Read more...

What to if I am on drugs to control high blood pressure but I want to join gym. Is it safe?

Depends on severity. Generally, regular aerobic exercise (along with a healthy diet) will be an important part of any high BP treatment regimen. However, you should discuss with your doctor the type of exercise you want to do. For example, if BP is very poorly controlled (i.e., very high), you should avoid high intensity static exercises like power lifting. Walking, biking or swimming would be great for you though. Read more...