http://discoveromaha.adam.com/ency/article/003698.htm Here is a web site that explains the plasa renin test. But with CAH - don't restrict salt intake. My ped endo orders three bloods test on one day - plasa renin; OH17 and the chem 8 (salt level). The OH17 must be done between 6 am and 8 am and no medications given before the test. It is mailed to a lab in California. This is important because of the hormonal surges. It is important to always give the cortef on schedule too - because of the hormonal surges in the am . Set an alarm clock in the morning and get up and give the meds. Your child does not make the cortisol naturally like we do and MUST have it in the mornings, afternoons, and evenings. .. three times a day.. especially before 9am (7 am ; 3pm, and 11 pm - is best). Florinef is given once a day for a child. A baby needs it twice a day and larger amounts and salt added to the diet. preston@kreative.net