Here's what someone else said about a Lantus low:

"The result, when I hit a vessel in my leg, was a drop in blood sugar from 180 to 30 in 1/2 hour!"

And someone else who noticed bleeding after removing the needle after her Lantus injection:

"About a half hour after dinner, I broke out in a sweat, . . . and suddenly it felt like someone punched me in the stomach. I managed to check my bg, and it was 35....oooops!" She said this has happened twice in 4.5 years.

Derek Paice has actually graphed a similar low. Click on Potpourri and scroll to the end of that document to see the graph. (I was too busy cooking fish to do any graphing when I went low.)

Why does this happen? It happens because when you inject Lantus into a blood vessel, it acts exactly like regular insulin (R). And a dose of R the size of a usual Lantus dose would certainly cause a low.

This happens because insulin has to be in the "monomeric" form in order to get into the blood and then get out again into the tissues to be active. Monomeric means each insulin molecule is separate, not bound to another molecule or anything else. Lantus is completely soluble in acidic solution, and the solution you inject is acid (this is why it sometimes stings).

When the solution encounters the neutral pH of the body fluids, it is no longer soluble and forms little precipitates (aggregates). These precipitates dissolve only slowly, and that's why the action is usually slow.

But if you inject into a blood vessel, even though the blood is at neutral pH, the rapid flow of the blood separates the insulin monomers before they have time to aggregate, and hence it works just like R.

These Lantus lows are fairly rare. But they do occur, and when they do, they happen about 30 to 45 minutes after you inject. Hence you should be cautious for about an hour after you take your Lantus dose, especially if you saw a drop of blood after you injected. If you don't expect them, you're more apt to be taken off guard when you're not in a position to treat them.

If you're going to drive after injecting Lantus, be especially careful, and pull over and test at the first sign that you might be going low. Lantus lows could be lethal.