To quantify the degree of fear of self-injecting insulin and self-testing of blood glucose in adult insulin-treated diabetic patients, the Diabetes Fear of Injecting and Self-testing Questionnaire (D-FISQ) was developed. The D-FISQ is a 30-item self-report questionnaire consisting of two subscales that measure Fear of Self-Injecting (FSI) and Fear of Self-Testing (FST). To test validity and internal consistency, the D-FISQ was administered to a sample of 266 insulin-treated patients (Type 1 and Type 2); four diagnosed injection phobic insulin-requiring diabetic patients also completed the D-FISQ. The minimal score was obtained on the subscales by 62% (FSI) and 57% (FST) of the population. The D-FISQ demonstrated high internal consistency, with Cronbach's as of 0.94 (D-FISQ), 0.94 (FSI), and 0.90 (FST). Spearman rho between fear of self-injecting and fear of self-testing was 0.59 (p < 0.001), justifying two separate subscales. Construct validity was confirmed by a correlation of 0.44 with Spielbergers Trait Anxiety Inventory (Spearman rho, p < 0.001). FSI-scores from the injection phobic patients were all > or =95th percentile, while three scored > or =95% on FST, indicating discriminative validity. Results confirm homogeneity and validity of the D-FISQ and suggest usefulness of this instrument in both clinical practice and research.