Nicole Galan, RN, is a registered nurse and the author of "The Everything Fertility Book."

Michael Menna, DO, is board-certified in emergency medicine. He is an attending emergency medicine physician at White Plains Hospital in White Plains, New York and also works at an urgent care center and a telemedicine company that provides care to patients across the country.

Giving yourself shots—of insulin or for fertility treatment, for example—requires proper technique and the right equipment. Needles and syringes come in different sizes, and some are better suited for certain uses than others.

The right needle size for your injections depends on how much medication you need, your body size, and whether the drug has to go into a muscle or under the skin. Your syringe also has to be big enough to hold the right dose, but not so big that it makes measuring small amounts difficult.

Not only will having the correct needle and syringe for you help ensure you get the correct amount of your medication, it will also make injections easier and less painful.

This article explains how needles and syringes are sized. It also provides some helpful tips for choosing the right size for the injection you need to give yourself.

Syringes are labeled based on how much medication they can hold.

1 cc is equal to 1 mL

If you are injecting your medication at home, you need to choose a syringe that will hold the dose you've been prescribed.

For example, if you're supposed to give yourself 3 ccs of a drug, you need a syringe that holds exactly 3 ccs or just a little more. If you use a syringe that can only hold 2 ccs, you would have to inject yourself more than once (using a brand new syringe and needle each time).

On the other hand, if you use a syringe that holds 15 ccs, it will be harder to see the cc markings. You could easily end up giving yourself too little or too much medication.

Needles are labeled differently than syringes. The packaging will have a number, then a "G," and then another number.

Here's an example: A 22 G 1/2 needle has a gauge of 22 and a length of half an inch.

If you need to inject yourself with a small amount of medication, it will usually be less painful to use a thin, high-gauge needle rather than a wider, lower-gauge needle.

For larger amounts of medicine, a wider needle with a lower gauge is often a better choice. While it might hurt more, it will deliver the drug faster than a thin, high-gauge needle.

The best choice for needle length depends on a person's size—for example, a small child would need a shorter needle than an adult. Where the needle will be inserted also matters.

Some medications can be absorbed just under the skin, while others need to be injected into the muscle:

You also need to think about how much body fat the needle will have to go through. A thinner person might be able to use an inch-long needle but someone heavier might need a needle that is an inch-and-a-half long.

Syringes can hold liquids or solids. You'll see milliliters (mL) marked on the tube for measuring liquids. You'll see cubic centimeters (ccs) for measuring solids. It's best to choose a syringe that holds the exact dose you need.

Needles are measured differently. The first number on a needle label is its gauge—how thick the needle is. Higher numbers mean thinner needles. The second number on the label is how long the needle is.

You'll need a longer needle if the medication is supposed to go into a muscle. You'll also need a longer needle for larger adults.

If you need to give yourself or someone else shots at home, you or a family member will need to learn how to do so safely.

If you have questions, reach out to the healthcare provider who prescribed the medication. Knowing the basics of needle size labeling will help you avoid making errors when you're giving the shot and replacing your supplies.

Beirne PV, Hennessy S, Cadogan SL, Shiely F, Fitzgerald T, MacLeod F. Needle size for vaccination procedures in children and adolescents. Cochrane Database Syst Rev. 2018;8(8):CD010720. doi:10.1002/14651858.CD010720.pub3

American Diabetes Association. Get a handle on diabetes medication.

Hamborsky J, Kroger A, Wolfe S, eds. Centers for Disease Control and Prevention. Epidemiology and prevention of vaccine-preventable diseases. Chapter 6: Vaccine administration. 13th edition. Washington, DC: Public Health Foundation

Salari M, Estaji Z, Akrami R, Rad M. Comparison of skin traction, pressure, and rapid muscle release with conventional method on intramuscular injection pain: A randomized clinical trial. J Educ Health Promot. 2018;7:172. doi:10.4103/jehp.jehp_216_18

Centers for Disease Control and Prevention. Vaccine recommendations and guidelines of the ACIP: Vaccine administration.

Doyle GR, McCutcheon JA. (2015). . Chapter 7.3: Intradermal and subcutaneous injections. In: Clinical Procedures for Safer Patient Care. Victoria, BC: BCcampus

Doyle GR, McCutcheon JA. Chapter 7.4: Intramuscular injections. In: Clinical Procedures for Safer Patient Care. Victoria, BC: BCcampus

By Nicole Galan, RN Nicole Galan, RN, is a registered nurse and the author of "The Everything Fertility Book."

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