Syringes

Syringes

Summary

Syringes are devices that people with diabetes use to inject insulin into body tissues. These injections help move glucose (blood sugar) into the cells from the bloodstream. The syringe consists of a hollow plastic or glass tube with a plunger inside, and a needle. The plunger forces the medication through the needle into the body just under the skin and into the fatty tissue. Measurement markings on the side of the tube indicate how much of a medication is being injected.

Syringe tubes come in many varieties. Patients match the size of their syringe tube with the strength and volume of the insulin they use. Needles also are available in various sizes and thicknesses. Patients should discuss these options with a physician to find the choice that is best for them.

Fears over using needles have long been a concern for some people with diabetes. However, recent advances have resulted in needles that are now smaller, sharper and thinner than those used in the past. In addition, needles are now treated with special silicone coatings that make injections less uncomfortable.

Despite the advent of alternative delivery methods, syringes remain the most commonly used technique for insulin administration, according to the American Diabetes Association.

Other injected medications include the glucose-raising hormone glucagon, synthetic amylin and the antidiabetic agents known as incretins.

About syringes

People with diabetes use syringes to inject insulin just under the skin (into subcutaneous tissue). Insulin allows glucose (blood sugar) into the cells from the bloodstream. The syringe consists of a hollow plastic or glass tube with a plunger inside and a needle. The plunger forces the medication through the needle into the body.

Today’s syringes contain needles that are thinner than older versions. In addition, needles now feature silicone coatings that make injections less uncomfortable than ever before. Despite the advent of newer insulin-delivery methods such as insulin pumps and inhaled insulin, syringes remain the most commonly used device for self-administering insulin, according to the American Diabetes Association.

Several varieties of syringes are available for people with diabetes. The type of syringe that is most appropriate differs from patient to patient and depends on several factors:

  • Insulin strength. Almost all insulin sold in the United States is U-100 insulin (100 units of insulin in 1 milliliter of solution), so patients will most likely need U-100 syringes, which correspond to that dosage strength. U-500 insulin requires U-500 syringes, which are different.
  • Insulin dosage. Patients should be sure that the syringe they use has the capacity to hold their present dosage. Some patients will find it easier to use a syringe that has a capacity that most closely matches their present dosage level. Others may want to buy a syringe that has additional capacity to hold any potential dosage increases in the future.
  • Needle length. Needles come in different lengths, such as 1/2 inch (1.3 centimeters), 5/16 inch (8 millimeters [mm]) and 3/16 inch (5 mm). The length of a needle can influence how deeply it penetrates the skin. Patients should consult a physician before choosing a needle length.
  • Needle gauge (thickness). Needle gauges range between 27 and 31. The higher the gauge number, the thinner the needle.

Patients should consult with a physician when trying to decide which syringe is appropriate for them.

Other self-injected medications include treatments for conditions including allergies, cancer, rheumatoid arthritis and multiple sclerosis, as well as several drugs that may be used by people with diabetes:

  • Glucagon. This glucose-elevating hormone may be prescribed by a physician as an emergency treatment to prevent diabetic coma resulting from severe hypoglycemia or insulin shock. The medication comes in a kit that includes a syringe. Other people should be trained in injecting the drug in case the patient becomes incapacitated.
  • Synthetic amylin. Also known as pramlintide (Symlin), this is the first drug other than insulin approved to treat type 1 diabetes, and it can also be prescribed for people with type 2 diabetes who use insulin. It must be injected separately from insulin in a different syringe.
  • Incretins. The first available medication in this class, exenatide (Byetta), is generally injected twice a day before meals with a prefilled device similar to an insulin pen. Incretins, also known as incretin mimetics, are approved to treat type 2 diabetes only.

Types and differences of syringes

Syringes come in many varieties. Patients choose a syringe with a tube capacity that corresponds to their insulin dosage level. If a patient’s insulin needs are increasing, then buying syringes that provide adequate size to increase the dose may be necessary. Syringe tubes are available in the following sizes:

Insulin dosageSyringe
30 units or less3/10-cc (cubic centimeter)
50 units or less1/2-cc
100 units or less1-cc

Other factors that differentiate syringes include:

  • Insulin strength. This is measured in units of insulin per milliliter. Nearly all syringes sold in the United States are made to hold U-100 insulin. However, patients who need very small or vary large doses may be prescribed other measurements, such as U-500 or U-10 strengths. U-40 insulin is commonly sold in Europe and Latin America.
  • Needle length. These include 1/2 inch (1.3 centimeters), 3/8 inch (9.5 millimeters [mm]), 1/3 inch (8.5 mm), 5/16 inch (8 mm), and 3/16 inch (5 mm).
  • Needle gauge (thickness). Needle gauges range between 27 and 31. The higher the gauge number, the thinner the needle.
  • Ease of drawing up insulin in a particular syringe.
  • Ability to easily read markings on the syringe tube.
  • Length of needle.
  • Packaging of brand.
  • Cost.

Patients comparing syringes should carefully examine the syringe dosage markings. In some syringes, one line is equal to one unit of insulin, but in others, each line is equal to two units of insulin. The right syringe will differ from patient to patient.

Many patients reuse the needles and syringes. This is often done safely. However, most manufacturers discourage this practice, and patients should consult with their physician before trying this. There are several circumstances in which a patient should not reuse a syringe. Patients should never reuse syringes if they have:

  • Illness
  • Open wounds on their hands
  • Poor resistance to infection

Needles should be capped when they are not being used, to ensure they remain clean. Patients should not clean needles with alcohol, as this removes the silicone coating that helps facilitate the needle sliding into the skin. Patients should dispose of a syringe when the needle is dull, bent or contaminated in any way. Patients should never let another person use their syringe, and should not use anybody else’s syringe.

People with diabetes need to make special preparations when they plan to travel to ensure that they will have access to syringes. It is prudent to get a physician’s prescription for syringes, as some areas require one to buy these supplies. Patients may also want to ask their physician to write a letter stating that they have diabetes and indicating the type of insulin they use.

Syringe aids

Many people with diabetes use their syringes daily and rarely or never encounter difficulties using them. However, others may struggle to master certain aspects of self-injections. There are a couple of aids that may help make injections easier:

  • Insertion aids. An automatic injector shoots a needle under the skin quickly and painlessly. Some models automatically release insulin, whereas others require the patient to press on the plunger. Insertion aids are a good alternative for those who have trouble injecting themselves because of conditions such as arthritis or diabetic neuropathy.
  • Infusers. A special catheter needle is used to insert an infusion tube into the abdomen. This tube remains in place for two to three days and insulin is injected into it.

Many patients with diabetes have visual impairments due to diabetic retinopathy, glaucoma or cataracts. These conditions may make it more difficult to measure dosages in syringes. There are several aids available for such patients, including:

  • Dose gauges. Some click for every one to two units of insulin measured. Others have Braille or raised numbers.
  • Needle guides and vial stabilizers. These devices help patients insert needles into insulin vials correctly. Some also allow patients to set a dosage level.
  • Syringe magnifiers. These enlarge the marks on a syringe tube.
  • Color-coded plungers. Some syringes have various colors that make it easier for patients to tell when they have the right level of medication.

Proper use of syringes

The American Diabetes Association recommends the following steps when administering insulin in a traditional needle-and-syringe setup:

Single insulin

  1. Wash hands.
  2. Choose injection site based on rotation plan and clean the site.
  3. Check insulin to make sure it is still good. Rapid-acting and short-acting insulins should be clear. Intermediate-acting and long-acting insulins should look cloudy without lumps or crystals. Dispose of any insulin that does not meet these criteria.
  4. Intermediate- and long-acting insulins need to be mixed. Patients should roll the bottle between their hands but should not shake the bottle (which can cause clumping). Rapid- and short-acting insulins do not need mixing.
  5. Pull back the plunger to draw an amount of air into the syringe equivalent to the number of units of insulin to be injected.
  6. Push the needle into the top of the insulin bottle while holding the bottle upright. Push down on the plunger to inject air into the bottle, and leave the needle in the bottle.
  7. With the needle still in the bottle, turn the bottle upside-down. Pull out the plunger, measuring slightly more insulin than required for the proper dosage.
  8. Tap the side of syringe, allowing air bubble to rise to the top. Push the plunger just enough to get rid of the air (and the extra insulin). Check to make sure there are no air bubbles, and that insulin is at exactly the right amount. When this is achieved, remove the needle from the bottle.
  9. With one hand, pinch an inch of skin at the injection site. Gently stick the needle just under the skin at the angle described by a physician. Press the plunger steadily until all the insulin is out of the syringe. The speed at which the plunger is pressed can be adjusted, according to the patient’s preference.
  10. When the syringe is empty, remove the needle at the same angle of insertion. Gently press on the injection site for several seconds to prevent the insulin from leaking.

Mixed insulins

  1. Wash hands.
  2. Choose injection site based on rotation plan and clean the site.
  3. Check insulin to make sure it is still good. Rapid- and short-acting insulin should be clear, whereas intermediate- and long-acting insulins should look cloudy without lumps or crystals. Dispose of any insulin that does not meet these criteria.
  4. Intermediate- and long-acting insulins need to be mixed. Patients should roll the bottle between their hands but should not shake the bottle (which can cause clumping). Rapid- and short-acting insulins do not need mixing.
  5. Begin with intermediate- or long-acting insulin. Pull back the plunger to draw an amount of air into the syringe equivalent to the number of units of insulin to be injected. Push the needle into the top of the insulin bottle while holding the bottle upright. Push down on the plunger to inject air into the bottle, and remove the needle from the bottle.
  6. Move on to the rapid- or short-acting insulin. Pull back the plunger to draw an amount of air into the syringe equivalent to the number of units of insulin to be injected. Push the needle into the top of the insulin bottle while holding the bottle upright. Push down on the plunger to inject air into the bottle. Keep the needle in the bottle and turn it upside-down.  Pull out the plunger to measure slightly more rapid- or short-acting insulin than needed.
  7. Keeping the needle in the bottle, tap the side of syringe, allowing air bubble to rise to the top. Push the plunger just enough to get rid of the air (and the extra insulin). Check to make sure there are no air bubbles, and that insulin is at exactly the right amount. When this is achieved, remove the needle from the bottle.
  8. Insert the needle into the intermediate- or long-acting insulin bottle. Turn the bottle and syringe upside down and pull the plunger to a measure equivalent to the exact amount of rapid- or short-acting insulin needed.
  9. With the needle still in the bottle, tap the syringe to force air bubbles to rise to the top. Try to remove the air bubbles without ejecting insulin. If large air bubbles are present, throw out the syringe and start over. Injecting large bubbles into the body can be dangerous. Also, pushing them out will change the insulin dose in the syringe.
  10. Once the right amount of intermediate- or long-acting insulin is present, remove the needle from the bottle.
  11. With one hand, gently pinch an inch of skin at the injection site. Gently stick the needle just under the skin at the angle described by a physician.  Press the plunger steadily until all the insulin is out of the syringe. The speed at which the plunger is pressed can be adjusted, according to the patient’s preference.
  12. When the syringe is empty, remove the needle and gently press on the injection site for several seconds to prevent the insulin from leaking.

Safe disposal of syringes

Syringes and the medications they contain are vital to the health of people with diabetes. However, unsafe disposal practices can make syringes potentially dangerous. Caution is necessary to ensure that people are not accidentally cut or stabbed by old needles.

Some states have laws that dictate how to dispose of syringes and other medical waste. Medical waste is defined as any material that touches human blood. Patients should learn and follow these regulations. The state department of health should be able to answer inquiries about these laws. Other good sources of information are the local refuse company, or city or county waste authority.

Used syringes and lancets should be stored in a heavy-duty plastic or metal container with a tight lid, such as an empty laundry detergent bottle or coffee can. Patients should make sure the lid is tightly secured before throwing the container in the trash. Be sure to mark the container with the words “Used Sharps” or other similar description.

Another option is to buy a special tool called a safe-clip that allows patients to safely clip the needle from a syringe. The safe-clip also catches the needles and contains them so the sharp edge is not exposed.  Once the needle is removed, the rest of the syringe can be tossed in with the regular trash. Safe-clips are available at pharmacies.

Patients should not clip needles off with scissors. There is a risk that the needle can shoot across the room when it is clipped, potentially injuring the patient or someone else, or becoming lost.  

Needle-destruction devices, sometimes called sharps-disposal devices, are also available from several manufacturers. These allow the patient to sever, burn or melt the needle.

Patients may want to carry a small plastic or metal box to store used needles when they are away from home.

Alternatives to syringes

In recent years, needles used to inject insulin have become shorter, sharper and thinner. In addition, a special silicone coating now makes it easier for the needle to penetrate the skin with a minimum of discomfort.

However, for patients who dislike needles, there are alternatives. In addition to the traditional syringe, there are several other methods used to deliver diabetes medications. These include:

  • Insulin pen. This device resembles a pen containing a cartridge and a short, thin needle on one end and a plunger at the other. Insulin pens have a dial that patients use to select the insulin dosage level they need. Some insulin pens use replaceable cartridges, and others are completely disposable.
  • Inhaled insulin. U.S. and European regulators in 2006 approved a powder, inhaled through the mouth via a device, as the first available form of inhaled insulin. It can be used by adult nonsmokers with type 1 diabetes or type 2 diabetes. Some patients, including those with type 1, still need to inject some long-acting insulin.
  • Insulin jet injector.  A high-pressure air mechanism sends a fine spray of insulin through the skin without an injection. Though needles are not used, some patients find the high-pressure air painful. In addition, some of the medication can be lost during delivery.
  • Insulin pump. This is a small, light device that the patient wears externally. The medication in the pump flows through a narrow, flexible plastic tubing with a needle at the end that is inserted just under the skin near the abdomen. These pumps deliver insulin throughout the day. Some models incorporate glucose meters, with a recent innovation being continuous glucose monitoring.
  • Implantable insulin pumps. Though still considered experimental in the United States, these surgically inserted devices are available in Europe.

Researchers are developing other methods of insulin administration. These include inhaled sprays, pills and patches.

Questions for your doctor regarding syringes

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about syringes:

  1. Which kind of insulin syringe do you recommend for me – which needle gauge, needle length, insulin dosage and insulin strength?
  2. Do you recommend any particular brand for me?
  3. Would I benefit from an insertion aid, infuser, dose gauge or other assistive device?
  4. Can I get training in syringe injections from a certified diabetes educator?
  5. Is it safe for me to reuse my syringes or needles?
  6. What are the advantages and disadvantages for me of syringe injections compared to alternate methods of insulin delivery, such as pumps and insulin pens?
  7. Are there any recent innovations that can replace syringe injections or make them less uncomfortable for me?
  8. Will I still have to inject some insulin if I use inhaled insulin?
  9. If I am prescribed glucagon, how is this injected? Should family members, friends, coworkers, school personnel or others be trained in using the syringe?
  10. If I am prescribed Symlin or Byetta, how do I inject it? Is it important that I use a new syringe for Symlin instead of reusing my insulin syringe?
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