Please clarify the ruling on taking insulin injections during the fasting hours. The doctor explained that I must take the insulin injection 30 minutes before meals. Is it permissible to take it during the final half hour of the fast?

There is no objection in Islamic law to taking subcutaneous insulin injections during the fasting hours and the fast would still be valid. This is because even though the insulin reaches an internal cavity, it does not do so through a natural orifice. Hence, the fast is valid in spite of this.
Allah the Almighty knows best.