The Final Word on Injections

Recent correspondence and commentary in “My Own Injection” in this publication reinforce what most of us who inject insulin daily know all too well about diabetes: so-called “professional” advice is either contradictory or just plain wrong. The common, well meaning, but just plain wrong admonition: “Don’t inject through clothing” is a fine example. Another is “Don’t reuse needles because you may develop an infection.”

The American Diabetes Association’s position seems mostly to address the concerns of (in this order) syringe manufacturers, “patients with poor personal hygiene,” the acutely ill, and those with hand tremors. They do however offer the sensible advice that “a needle should be discarded if it is noticeably dull or deformed.”

So what should you do? Inject through your jeans or other clothing? Reuse needles and syringes?

The usual explanation for advising not to inject through clothing is that this will cause infection. Indeed, if you’re a patient with extremely poor personal hygiene, this would be sound advice. I have yet to come upon any patient, however, whose clothing has been so grossly contaminated that there would be a risk of developing an infection by injecting through it. Personally, I’ve been injecting through shirts and undershirts since 1973 and have never had an infected injection site (not even once). I’ve taught all my insulin-using patients how to save time by doing the same thing, with the most serious complaint the rare blood spot on the shirt. My grand total of shirt injectors is about 1,500 people. But what about jeans injectors? I pinch the thighs of all my diabetic patients before teaching them how to inject. I have yet to find one with adequate subcutaneous fat for injecting into the thigh. A recent study of many diabetics and non-diabetics supports this finding and suggests it may be much less common in non-diabetics. So don’t inject into your thighs with or without jeans—unless you specifically want an intramuscular shot of rapid-acting insulin in order to bring down an elevated blood glucose level fast.

What about injecting through your jeans into your butt? Fine, but don’t go through a pocket or through a thickness of clothing that exceeds 1mm or the injection may be intra-dermal instead of a subcutaneous. This can be painful and may involve less predictable absorption of insulin. Do you need calipers to measure the thickness of your clothing? No. Most jeans—except on the seams and pockets—are probably less than 1mm thick.

When using your butt, there’s no need to grab a hunk of fat. I’m sure you have adequate butt fat thickness to prevent an intramuscular injection. Remember, however, that except for special situations (described in my book Diabetes Solution) injections must be into subcutaneous fat and not into muscle. This means that it usually must be possible to grab a hunk of fat before “throwing” in the needle. (The speedy and painless “throw method” of injection is also described in Diabetes Solution.) If not, choose a site with more fat.

What about the reuse of insulin syringes? Should you or shouldn’t you? All of us who have tried it know that painless injections are easy, with needles dull or sharp, if you throw the needle in rapidly. So reusing needles need not cause pain. Just don’t share them.

Likewise for the claims that reuse causes infection. I’ve seen hundreds of people who had been reusing syringes before visiting me yet none had experienced infection at an injection site. What’s your experience?

When I started practicing medicine in 1983, I soon began to hear complaints from patients that their insulin no longer worked. When I examined used insulin vials, it was apparent that the clear insulin (called Regular or Crystalline) had turned cloudy. This only occurred when patients reused their syringes. I sent some of these cloudy vials to an insulin manufacturer in Denmark for analysis. The report I received was that the cloudy material was polymerized insulin. This meant that many insulin molecules had clumped together to form inactive particles. I was also told that this phenomenon had never been seen before. A little thought gave an explanation: It was known even in those days that insulin could polymerize in the tubing of insulin pumps. The narrower the tubing bore, the more problems with polymerization. Needles of insulin syringes have much narrower bores than pump tubing and will, therefore, facilitate more rapid polymerization. After giving an insulin injection, a small amount of insulin remains in the needle where, over the course of a few hours, it polymerizes to some degree.

When air is drawn into the used syringe and injected into a vial of insulin for the next dose, the polymerized insulin can be expelled into the vial. There it will serve as a seed for more polymerization. If this process is repeated sufficiently, any vial of clear insulin will become slightly to very cloudy and will be relatively ineffective at lowering blood glucose. With cloudy insulins such as NPH, Lente and Ultralente, the additional cloudiness will not be visually apparent.

Why did this phenomenon only affect my patients? The difference was in the dosage. Those were those days before DCCT (the 10-year Diabetes Control and Complications Trial, which ended in 1993). In those days, many diabetics were taking only one or two large doses of NPH insulin a day to cover their high carbohydrate diet. My type 1 patients, on the other hand, were taking a minimum of five small doses of insulin daily. In addition to the five daily shots, they would take doses of short acting insulin (Regular) as small as 1/2 unit to bring down slightly elevated glucose levels. It’s safe to estimate that my patients were taking about six small injections for every one or two daily injections that other type 1s were taking.

Furthermore, since my patients all followed a very low carbohydrate diet, their total daily insulin dosage was about a half or a third of that used by other type 1s. Why does this make a difference in reusing syringes and needles? What makes a difference is how many times you put the needle back into the vial and inject air (along with polymerized insulin).

A typical diabetic might take 20 injections of 50 units in order to use up a 1,000-unit vial of insulin. On the other hand, one of my patients might take 20 units daily divided into 6 shots for a total of 300 injections per vial—l5 times as many as other diabetics.

If they reused their syringes, they would therefore inject 15 times as much polymerized insulin into a vial. This is why only my patients found their clear insulin turning cloudy and losing efficacy. Nowadays, many more patients are taking multiple small injections thanks in part to low carbohydrate diets. Thus, the likelihood is great that my patients will no longer be the only ones to spoil their insulin by reusing syringes.

How can you reuse syringes without spoiling your insulin?

  1. Flush your syringe with sterile injectable water or sterile injectable saline or insulin diluting fluid (not made for Glargine insulin). Check with your pharmacist about obtaining vials of any of these fluids. The insulin diluting fluid vials are obtainable at no cost from most insulin manufacturers.
  2. Use two syringes: one for injecting air into your insulin vials once weekly. A second for drawing out insulin. Never inject air or insulin back into a vial with the second syringe. Any excess insulin in a syringe can be expelled into the air over a sink–never back into the vial. This approach may be more practical than maintaining a fresh supply of sterile fluid for flushing syringes.

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Dr. Bernstein has had type 1 diabetes since 1946. His latest books are The Diabetes Diet and Diabetes Solution, both published by Little, Brown and Co. He is Director of the Diabetes Center in Mamaroneck, New York.

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