When my 14 year old is at 400 mg/dl [22.2 mmol/L], she feels sick. Then, when she is coming down she gets a headache. Is the headache due to the rapid reduction in blood sugar? Was her brain swollen from the ketones and high blood sugar even for that brief time? If she has “sick” symptoms, is that a sign that her situation is more serious than a high number without sickness?