Can someone tell me what a normal progesterone level is for a non-pregnant woman?

How precise u want?: The levels vary considerably depending on your age, stage/time ofyour menstrual cycles, and whether you on the pills etc...Follow this link: http://en.Wikipedia.Org/wiki/progesterone#levels this provides an easy to read and interpret table/range for this incredible hormone. Have fun and good luck..

When?: Depends on when during her cycle it is measured. Prior to ovulation levels are low, typically less than 1 to 2 ng/ml. Soon after ovulation levels will be greater than 2 ng/ml and up to 25, 30 or more. In the second half of the cycle (luteal phase) Progesterone is secreted in pulses and levels vary widely; i therefore think the idea of 'normal' doesn't help much.

Varies a lot: I agree with the other answers. Progesterone (p4) is secreted after ovulation in pulses. We have several methods of measurement: mid-luteal (7-8d after ov: >= 10-15), pooled measurement (get 3 samples after ov on different days, mix blood and level >10 normal). Some use endometrial biopsy as substitute for blood test. All are imperfect and docs vary in their choice of test and normal values.