Newborn jaundice - how to improve it

My nephew left the hospital last week - jaundice level at 230 on his first day. After one week, it goes up to 270... (border line is 300) Our family doctor advices to send him back to hospital. We are worrying the baby and we have no idea how to control or improve it.... we tried breastfeeding more often like 60ml every 4hours these 2 days and we tried use formula milk....etc. Any experienced mum can share your experience and methods?