“How bad is a blood pressure 140/90?”

Today a systolic (upper number) BP above 130mmHg is elevated and a diastolic (lower number) BP above 85mmHg is also elevated. So, in your case 140/90 mmHg is elevated. However, a single BP check is NOT diagnostic of hypertension. In a case where you have an elevated BP reading, you should be re-evaluated by your doctor, or yourself at home or another professional who can check your BP regularly. Keep a diary of all of the readings. Write them down. Bring them to your doctor's office so he/she can see them. The doctor will be able to discern where are you standing in regard to the BP scales. Even if you have elevated BP, initial treatment will be to do some diet and exercise. However, you may need other studies to evaluate your condition.

Having hypertension is a very serious thing. It can predispose the person to have strokes, heart attacks, and kidney problems. And remember hypertension doesn't cause symptoms.