Why is it called "blood sugar level"? Shouldn't it be "sugar blood level"?

I was getting through a sinus infection over the past week.  With a sinus infection comes headaches and some lightheadedness.  I learned over the years that increasing my blood sugar levels while sick helps with headaches, especially in the morning when I first wake up.

Suddenly, something occurred to me.

In English, the statement "X Y level" or "X Y ratio" would translate to the ratio of "X / Y".  Or atleast that's how I would interpret it.  For example, with "salt water", the salinity going up or going down matches the ratio "salt / water". 

However, that's not what "blood sugar level" means, it actually means the "sugar / blood" ratio.  So it's backwards.  Like when someone says you have a "high blood sugar level", it means the "sugar / blood" ratio has gone up.

I was thinking of other phrases in English that translate this way but couldn't think of any.

I was thinking of other counters, and the only other one I could think of was in cooking.  When people speak of ratios it's often something like "you want a 3:1 ratio of flour to sugar".  You do technically speak the part levels, but again, it's spoken as "X / Y" and not "Y / X".

Update 7/6/15:

I just thought of another example, "blood alcohol level".  Similar to "blood sugar level" it means "alcohol / blood".