Hi Katherine This is my own understanding. if you want to assess zinc deficiency then it means whatever results you will get, you will compare them with the reference values for optimal zinc status. I am not sure why you had chosen 6-9moths in the first place, but the reference values for children are in these categories 1.6-11 month 2. 1-3 years 3. 3-6 year. There are more categories as the child grows older so i am sure that if 6-9 months is proving to be a problem you can increase it to 11 months or you can assess 1-3 year olds. Hopefully i have answered your question Regards

thanks a lot