neonatal diabetes mellitus (ndm) is a type of diabetes. it happens during the first 6 months of human life. infants with this condition do not produce enough insulin. this causes an increase of blood sugar. ndm is often mistaken for the much more common type 1 diabetes, although type 1 often happens after the first 6 months of life. in almost 60% of those with ndm, this condition lasts their whole life.