Father-in-law Is 90 Years Old, Stage 4 Kidney Failure That

Father-in-law is 90 years old, stage 4 kidney failure that has been stabilized at "20%" for 3 years. Recently started Metoprolol tartrate for arrhythmia. Not sure he is taking correct dosage yet because he is very dizzy upon changing position and BP is running about 150/59, pulse about 51. We see the doctor in a week to make adjustments, but should I call the doctor sooner and discuss the dosage?