Hi. Although 18mmol is high I would not panic but keep a close eye on it. Drink plenty of water, keep the carbs down and test frequently. I was 25 yesterday due to a big mis-match between the carbs and Bolus insulin which rather scared me but with a the right Bolus shots it came back down. What meds is your partner on? He/she could possibly be LADA (T1) and not T2 with those high levels.