I Have Been Prescribed ATENOLOL For High Blood Pressure. 25

I have been prescribed ATENOLOL for high blood pressure. 25 mg. I am afraid to start taking this medication but my blood pressure is fluctuating between 131/95 to 151/92 sometimes it's higher. My heart rate is between 80 and 102 depending when I take it. I am afraid to start taking this medication due to I have a lot of medication sensitivities. Is it OK to cut this pill in half to see if I can tolerate it?my doctor told me to take it only if my bottom number was 90 or above. Is this true?