Try all of the following: make sure that your hands are clean and dry; make sure that the strips are good and have not been exposed to excessive moisture, the strips should be white where you apply the blood; make sure the strip is inserted completely into the machine; make sure you wait for the prompt to apply blood, do not apply the blood too early. Have these strips been exposed to excessive heat? That is, have the strips and left in a vehicle for an extended time in direct sunlight? Hope that helps!