Hi My Husband Is On Warfarin For Blood Clots So

Hi my husband is on warfarin for blood clots so it has been for the last three years and he has been stable for well over 2 years. One of his last readings was 3.7 they stopped the warfin for one day then he went to 4mg next test was 2 so he stayed on 4mg and now this one is 1.7. this testing has been over 2 weeks. Last night he was crying and he is really down so is there any link between low inr and this very out of character behaviour.