this is what I found online:
In general, the midluteal (middle of the second half of the cycle) progesterone in a non-pregnant patient is 8 to 10, but can be as high as 20 ng/ml. In a pregnancy cycle, it should be greater than 10 to 12 ng/ml to have a better chance of a good pregnancy outcome, but in general, we like to see 16 or over.
and this
The Results of the Progesterone Test
The progesterone level should be more than 15 ng/ml about 7 days after ovulation. This suggests that the corpus luteum is functioning normally. A low Day 21 progesterone levels suggests the cycles was anovulatory ( no egg was produced).