Getting your blood drawn at the appropriate time in the day and in your cycle can be really helpful, to determine what’s really going on in your body.
Some lab tests you should be fasting for, others don’t really matter if you have eaten or not.
Some of the lab tests recommended should be taken in the morning after fasting overnight, such as: blood glucose, insulin, and am cortisol. The cortisol is more a timing issue of taking the lab sample within 30-60 minutes (or as close as) of waking and not so much because you need to have fasted.
LH and FSH are helpful to look at during the beginning of your cycle. Day 3 is optimal.
Male hormones don’t change too much depending on your cycle. If they are elevated, they are typically elevated, doesn’t matter if you are on your period, ovulating, or about to bleed.
You really only make an appreciable amount of progesterone if you have ovulated or are pregnant. So, if you have it tested early in your cycle before ovulation would take place, it won’t tell us much. Likewise, if you have a longer cycle, more than 35 days, getting a day 21 progesterone won’t tell you anything more than you didn’t ovulate “yet”. I always recommend women get progesterone tested seven days after ovulation. See my blog on ‘The power of ovulation’ and ‘Truth about getting pregnant on day 14’
Getting any other tests done like oestrogen, prolactin, AMH, SHBG, vitamin D or vitamin B12…. these are also tests you can have taken any time. Something like oestrogen is helpful to know what point of your cycle you were in during testing, and based on symptoms, your practitioner might request it to be drawn at a specific time.