There is currently a lack of valid instruments to measure adolescent diabetes numeracy. The Diabetes Numeracy Test (DNT) was adapted for type 1 diabetes and was administered to 2 samples of adolescents. Sample 1 was administered the 39-item version of the DNT (DNT-39) with measures of self-management, responsibility, reading, and glycemic control (A1C). Sample 2 was administered the 14-item version of the DNT (DNT-14) with measures of self-management, responsibility, problem solving, and A1C. Both versions of the DNT showed adequate internal reliability. In Sample 1, the DNT-39 and DNT-14 were related (r = .87, p = .001), and both DNT versions were related to parent education (for DNT-14, r = .31, p = .02; for DNT-39, r = .29, p = .03) and reading (for DNT-14, r = .36, p = .005; for DNT-39, r = .40, p = .001). In Sample 2, the DNT-14 was related to A1C (r = -.29, p = .001), reading skills (r = .36, p = .005), diabetes problem solving (r = .27, p = .02), adolescent age (r = .19, p = .03), and parent education (r = .31, p = .02). In combined analyses, 75% of items were answered correctly on the DNT-14 (range = 7-100), and performance was associated with age (r = .19, p = .03), pump use (r = .33 p = .001), and A1C (r = -.29, p = .001). The DNT-14 is a feasible, reliable, and valid numeracy assessment that indicated adolescents with type 1 diabetes have numeracy deficits that may affect their glycemic control.