I need to know if my car needs coolant is on 187
Need to check the level first, if low add some, Look to see if it reaches the line on reservoir, hot or cold line as determined to read when hot or cold. If coolant old or never changed out or flushed then do a coolant flush, also check the freeze point, if too high or/and if its dirty change it out for new.
but 187 degrees is within normal range for most as long as its not fluctuating up and down too much. Also if doing coolant change have the thermostat replaced and hoses checked and the reservoir lid checked for leaking and/or fan(s) operating as intended "Coolant Temp switch".