A Trial Investigating the Concentration in the Blood of NN1250 in Children, Adolescents and Adults With Type 1 Diabetes

Inclusion Criteria: * Male or female aged 6-65 years (both inclusive) * Type 1 diabetes mellitus (as diagnosed clinically) for at least 12 months * Body mass index for children: 15.0-20.0 kg/m\^2 (both inclusive), for adolescents: 18.0-28.0 kg/m\^2 (both inclusive) and for adults maximum 30.0 kg/m\^2 Exclusion Criteria: * Subject who has donated any blood or plasma in the past month or more than 500 mL within 3 months prior to screening * Not able or willing to refrain from smoking during the inpatient period * Female of childbearing potential who is pregnant, breast-feeding or intends to become pregnant or is not using adequate contraceptive methods