Yes. If your blood pressure has come down because of health and lifestyle management, your agent can submit proof of your improved blood pressure readings to your insurance company and request a lower rate class on your life insurance policy.
Your agent will likely submit a new application to another insurance company as well as a backup in case your current carrier is unwilling to put you in a more favorable health class.
Moreover, if your high blood pressure worsens after your policy has been issued, your insurance company cannot increase your rates or reduce your death benefit.