Complex sentence: Private and public insurers all have their own drug formularies through which they set coverage limitations which may include referral to the insurance company for a decision as to whether the company will or will not approve its share of the costs.
Split into simpler sentences: Private and public insurers all have their own drug formularies through which they set coverage limitations. They may include referral to the insurance company for a decision as to whether the company will not approve its share of the costs.