Hypoglycemia is defined as low blood sugar.  Hypoglycemia manifests as hunger, sweating, tremulousness and, if severe, with confusion, disorientation and, on occasion, loss of consciousness.

What, exactly, "low" blood sugar is, varies to an extent from person to person and indeed, from dictionary to dictionary, but is generally said to be a blood sugar below 3.6 to 3.8 mmol/l.  I don't want to be too specific about the precise number because different people experience symptoms at somewhat different values and some perfectly healthy people can have technically low readings but be perfectly fine.  (I find it fascinating that some marathon runners have been found, mid-race to have blood sugars in the two's with NO symptoms; amazing, eh?).  In any event, most people with diabetes who are on therapy with pills ("oral hypoglycemic agents") or insulin are at risk for hypoglycemia.

By the way, not all "diabetes pills" lead to low blood sugar.  Sulfonylurea drugs (such as glyburide) or meglitinides (such as Gluconorm) can, whereas acarbose, metformin, glitazones (such as Avandia or Actos), GLP-1 analogues and DPP-4 inhibitors do not.

Here's another "by the way:"  contrary to what many people think, hypoglycemia in someone who does NOT have diabetes, does NOT lead to or cause diabetes!  Note that I both bolded and capitalized the word "not" so I must really, really, mean this.

Most episodes of hypoglycemia are mild and easily treated.  The Canadian Diabetes Association guidelines recommend:

If an episode of hypoglycemia is so bad that it has made you pass out, you should be given an injection of a substance called glucagon.  What this means, however, is that whomever is helping you out would, of course, need to know how to do this.  What I recommend is that if you have diabetes and if you have a history of severe hypoglycemia (to the point of making you unable to look after yourself during an episode) you should be given a prescription for glucagon (a "glucagon kit;" pictured left) AND you should take your spouse (or capable child or parent or whomever it is that is likely to have to look after you should you lose consciousness) to the pharmacist and have the pharmacist explain to them how to give you the glucagon.  Even if you have been given glucagon, I would still recommend an ambulance be summoned in case you need further assistance.