Generally, a 50% blockage of a carotid and if you haven't had any signs or symptoms of a stroke, it is usually recommend that the condition be treated with lifestyle changes and medication. Eating healthy foods, exercising, losing weight and, in some cases, lowering the amount of sodium in your diet, may help slow the progression of carotid artery blockage (stenosis). Cigarette smoking is a risk factor for carotid artery disease and stroke. If you use tobacco, you should permanently stop.
Controlling high blood pressure is a major risk factor for stroke among people with carotid artery disease. Bringing your blood pressure down to approximately 120 over 70 mmHg can reduce your risk of stroke significantly. Controlling your blood sugar levels if you have diabetes and lowering your cholesterol levels with diet, exercise and, if necessary, a statin drug, if you have high cholesterol may reduce your stroke risk, as well.
I don't believe 50% blockage would be considered normal as that is almost in the range for a medical concern but can be effectively treated with life style change, etc.
Thank you for your question and I wish you well going forward. Take care,
Ken