Blood Plateletes

So... my dad's blood platelets are SUPER low according to his oncologist. Low as in the low 40's. What can we do about this? Is there anything any of you would recommend? Also, has anyone had any issues with blood clots? The doc recently did an ultrasound of Pop's leg and low and behold... ANOTHER clot. Not severe enough to slow him down, but enough of a build up to show on the ultrasound. Anyway, just thought I'd put my questions out there. Any info would be appreciated!

Thanks!