Is there an alarming issue when you gain weight about 8 pounds at age 46?

Yes. Actually, yes. Forties is the common time for onset of chronic (though often silent for years or decades) or degenerative disorders, such as atherosclerosis, or inflammatory disorders like osteoarthritis. It's not the eight pounds that is alarming, but what changes in your lifestyle, or lipid panel, or potential for diabetes that is. So get yourself a thorough checkup, and stop at single digits.
Yes. An 8-lb weight gain over a few weeks is "alarming", but a gain of 8-lb over a year or two may not be worrisome. In both cases, a doctor can check to see if there is a medical problem. Without medical problem, women around menopause may still gain weight due to hormonal changes or due to a lower resting metabolic rate (rmr). Exercise may raise one's rmr. Eating fewer calories per day will help.