Routine or preventative blood or urine tests can be performed with test strips. These are dipped into the test liquid, and a colour-forming chemical reaction occurs on the eagent strip. The colour formed allows the concentration of glucose in the test liquid to be estimated approximately.

On the test strip we can distinguish a protective net (1), the reagent paper (2), absorbent paper (3) and the base foil (4).

In blood sugar determination the glucose is enzymatically oxidised (by the oxygen in the air) to D-gluconolactone, with the release of H₂O₂ . The H₂O₂ reacts further with a yellow dye, catalysed by a peroxidase enzyme, to form a brown end product.