Low, not low enough
When normal IgA levels are determined, they are usually based on the average values of the population tested and the age of the patient.
There are usually 2-5 % of normals that are included in the low range. You can relax. Even though 38 may be low, it is high enough to protect you against infections. If you have levels less than 20 mg/dl then you would be at risk for recurrent infection.