I do my cardio first thing in the morning before I eat and right now am doing it every day. However, hiit cardio would be maybe every other day.
I do a 2 minute warmup on the treadmill then do 8 sets of 15 second sprints followed by 45 seconds of jogging. This equals 10 minutes
Then I do 25 minutes of a steady, moderate paced jog or walk,
Then sets of 1 minute sprint followed by 1 minute jog = another 10 minutes
This will give you 45 minutes of great hiit cardio
The days I don't do hiit, i just do a moderate walk on the treadmill keeping my heart rate around 113 which is what's suggested for my age group