Q: My daughter, who is 3 months old, suffers from CAH due to 21-hydroxylase deficiency. We check her sodium and potassium once a week but I think this is harmful for her. Are there any methods to check her electrolyte serum at home more simply than going to a lab?

A: It is usually necessary to check sodium and potassium frequently in the first month or so of life, until the levels have stabilized and the treatment doses do not need adjustment. Once you get the levels stabilized, though, there isn’t usually a need for such frequent checks. Usually every 3 months (along with adrenal hormones and plasma renin activity) is adequate. Perhaps your daughter is not gaining weight, or has difficulty taking her meds and that is why your doctor is checking more frequently? If that is not the case, perhaps you could ask your doctor if the blood draws could be spaced out now that she is 3 months old and stable on her meds. In terms of the routine labs that are checked every 3 months, however, unfortunately there is not a simpler way to do it.