@bluey1234 every couple hours, I’d say 2-3 hours max before getting up and take a small walk.
Source NHS:
“If you are travelling to an altitude of 4,500m or higher and are taking the combined oral contraceptive pill (COCP) or using a patch or vaginal ring for contraception, you have an increased risk of developing blood clots (thrombosis).”
You can find more info on this online xx