One of the misconceptions people most frequently tell me that they have had about diabetes, along with "At least it's manageable" and "You must have some sweet tooth!", is that you can take insulin by mouth.
And why shouldn't they think that? From the very beginning of oral hypoglycemic agents, the press has confused medication to improve the body's natural ability to make and use insulin with insulin itself.
Not only that, but when insulin was being developed by Banting et al, they did try giving it orally before it occurred to them that it might need to be injected.
But insulin is digested if you try taking it orally. It will not lower blood sugar. It might, maybe, alter the way that the body's immune system deals with insulin- it has been tried for prevention of diabetes- but it does not work as insulin.
But there are lots of ways to bypass the digestive system.
You can inject insulin into a vein- only regular insulin is approved for this use, and since intravenous injections are kinda dangerous and tend to damage veins over time, and you kinda need your veins, and plus you don't usually want to get your insulin that fast - people don't usually take insulin this way. Insulin is given through IV mostly in hospital settings either in treatment of DKA or during surgery, although it may be given IV at other times.
Dr. Bernstein of the low carb diet recommends IV insulin as a method of getting blood sugar down as quickly as possible but frankly I think the risks outweigh the benefits by a long shot (get it? a long shot!)
You can inject insulin into your skin. It will form a painful bubble before being absorbed into the fat layer underneath and from there to the blood stream. That hurts, is hard to do on purpose, and leads to slow and inconsistent absorption. As far as I know, people mostly do this by accident, and not very often even then.
The most common and recommended way of getting insulin into people is by injecting into fat. The trickiest part of this is that some people (like me) don't have a whole lot of fat to inject. Injections into fat have all the problems of other injections: they can hurt, cause bleeding, cause scarring, and damage tissue. But at the moment it seems to be the best bet. Injecting into fat generally causes a gradual and consistent release of insulin into the blood stream.
Another place you can inject insulin into is muscle. Personally I do this an awful lot, mostly by accident. I can tell because I feel resistance from the needle as it breaks through. Injecting into muscle has both the advantage and disadvantage that it causes quicker absorption of insulin. It may also be less regular, because using the muscle will change how the insulin absorbs. Injecting muscles tens to cause more bleeding, scarring, etc.
A great study I recently read about skin, fat, and muscle thickness is here. The most important take away is that skin thickness is 1mm- 4mm, and that especially in skinny and male adults, it is not unsual for the fat layer in the arm and thigh to be thin enough that shots intended to be subcutaneous will be intramuscular even with very short needles, if they are used at a 90 degree angle. The other take away that is important is that in almost 400 people, more than half of them overweight, they did not find a single person who would be injecting into skin if xe injected at a 90 degree angle even with the shortest needles on the market- 4mm.
Another misconception I hear a lot is that insulin injections involve needles like you get your immunizations from. Generally they don't; you can, like I just said, use a teeny tiny needle- 4mm is about a sixth of an inch. You can also inject without a needle at all if you're really needle phobic.
You can inject with various lengths and widths of needles; you can use syringes, insulin pens, jet pens without any needles or cannulas (IV or SC) introduced by a needle which is then removed.
Of course, many people think that there ought to be a better way to get insulin.
Exubera was the first insulin on the market that was not intended to be injected; it was inhalable. Unfortunately, it was poorly marketed, expensive, gave boluses only in increments of three units, and short acting. It was removed from the market on the grounds that it wasn't making enough money; follow up studies of exubera suggest it may have increased risk of lung cancer.
Despite this, research on inhalable insulin continues (Technosphere Inhalation Insulin is in phase three studies) and it is clear that, whatever, the downsides may be, it is possible to lower type 1 diabetics' blood sugars via inhalers.
You cannot currently legally buy insulin to inhale; the only ways to get some currently is either to have a stash from when Exubera was on the market (not so long ago) or to participate in a study for Technosphere Inhalation Insulin, which is being studied currently only in type 2 diabetics who are taking Lantus but no meal time insulin and who need a meal time insulin.
Insulin has also been shown to work when given in suppository format, although I haven't heard much enthusiasm about that from the diabetes community generally, for the obvious reasons that sticking insulin up your butt is a heck of a lot less discrete than taking a shot, and many of us suspect it might be even less pleasant. There are currently no trials happening with this concept and I'm doubtful that there ever will be.
Animal studies have also shown that insulin can be given, with other chemicals, in eyedrops and will lower blood sugar. Insulin alone doesn't work. I'm not sure if this will ever be useful to humans. May be.
And of course, I may have dismissed the oral route too quickly. I could not find any studies on oral insulin in humans taking place currently. This article claims that there are currently oral insulins in development that should work as bolus insulins. We'll see.
In conclusion, insulin cannot currently be bought to be taken any way other than through infusion or injection. Insulins that may work as bolus-only insulins might in the next ten years be available in non-injectable formats, but the basal needs of type 1 diabetics will probably continue to be met only by insulin injected or infused.
And thanks for the kind sentiments on the previous post!