Is it permissible to check blood sugar during Ramadan with Accu Chek?

As salam Alaekum, My father is diabetic and he is on medication,recently his blood sugar level are very high and still not in control,he keeps all the fasts of ramzan,during the fasts there chances that his blood sugar level may go down the normal value,for that purpose during Roza is it allowed to check his blood sugar level with Accu Chek(A Procedure in which the finger is pierced with a needle and a drop of blood comes out and that drop has to be put on machine for testing) or that will cause any harm to his roza. Allah hafiz