SINCE injectable insulin was first used in 1922 to lower the blood sugar levels of diabetics, it has saved millions of lives. In large enough doses, however, insulin is a deadly poison.
Injection of one-tenth of a millilitre would cause your blood sugar to drop enough to leave you shaky, sweaty and unable to concentrate, though you would soon recover. Half a millilitre would probably render you temporarily unconscious, and 10 millilitres would almost certainly be fatal.
One reason insulin kills is that the brain, unlike the rest of the body, can only function on one energy source: glucose. If…
