Hi Lut,
I think the first thing I would do is insist on another blood test. 366 sounds unbelievably high. Make sure the blood is drawn after fasting overnight, and that your daughter gets a good night of sleep before the test and no workouts or exercise that morning.

Is she on any other medications - some of these can cause a false high. Heredity is also a big possibility and probability if it truly is high.

If the retest is similarly high - the doctors will advise you - but there ARE some things she can be doing. Fish and Garlic oil (our grocery stores even carry these things) like sammy101 mentioned can be helpful. Exercise is helpful. Hubby was able to lower his total cholesterol by 80 points in only six weeks simply with fish oil capsules and oatmeal every single morning. Oats lower cholesterol for some reason!

Also - consider her HDL and LDL readings of cholesterol since a higher HDL (50+) is actually positive thing and low LDL (under 130) is a good thing and both of these readings can help make the total reading less alarming. Also - triglycerides are a 4th number they should check for and under 150 is the magic number for that reading. The numbers vary somewhat by lab but these are the values I learned.

Most of all - I would really want another set of labs drawn (LDL, HDL, Triglceride and Total) as this could easily be a false reading. My 2 cents.

Hoping for the best! Remember - if she really is high - there are plenty of things to do and assorted medications (quite likely also!) to try. I understand the fear that something could be wrong with your 15 year old daughter - scary!! I would also freak - but then think logically and have some retesting done, then get medical advice and be glad to find the problem early - OK??

(((Hugs))) to you