Intramuscular Injection (IM): What It Means
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[Glossary · Injecting]

Intramuscular injection (IM)

Also called IM injection, IM shot, into the muscle · Reviewed

Definition: An intramuscular injection (IM) puts medicine deep into a muscle, below the fat layer. Most testosterone injections in the US are labeled this way. The Depo-Testosterone (testosterone cypionate) label says it is for intramuscular use only, given deep in the gluteal (buttock) muscle, and never into a vein.

What the label says

The Depo-Testosterone label states that the injection is for intramuscular use only and should not be given intravenously. It says intramuscular injections should be given deep in the gluteal muscle. For replacement in men with low testosterone, the label lists 50-400 mg every two to four weeks, adjusted by the prescriber.

It comes in two strengths, 100 mg/mL and 200 mg/mL, stored at room temperature (20-25°C, 68-77°F) and protected from light. The 10 mL vial of the 100 mg/mL strength is labeled multiple-dose, so one vial covers many shots.

Worked example

IM doses are measured in milliliters, so the vial strength decides how much liquid one dose is. This is arithmetic only, not a dose suggestion.

The same 100 mg from two vial strengths

  1. At 200 mg/mL: 100 mg ÷ 200 mg/mL = 0.5 mL.
  2. At 100 mg/mL: 100 mg ÷ 100 mg/mL = 1.0 mL.
  3. A 10 mL vial at 200 mg/mL holds 2,000 mg. At 100 mg per shot that is 20 shots.

If you switch vial strength and keep drawing the same volume out of habit, the dose doubles or halves. Logging the dose in milligrams, along with the vial you drew it from, makes that kind of slip visible.

Common mix-ups

  • Route is product-specific. Xyosted, a testosterone enanthate product, is labeled for subcutaneous use in the abdomen and says to avoid intramuscular injection. One label does not speak for another.
  • IM vs IV. Intravenous (IV) means into a vein. The Depo-Testosterone label says not to give it that way.

Read more on Dose Track: Testosterone cypionate guide · Cypionate vs enanthate · Weekly vs twice-weekly TRT

General education drawn from labels and published studies, not personal medical advice. Your prescriber, pharmacist and the label that came with your product are the final word.
Subcutaneous injection (SubQ)A subcutaneous injection (SubQ) puts medicine into the layer of fat just under the skin, above the muscle.… Testosterone esterA testosterone ester is testosterone with a fatty acid chain attached, such as cypionate or enanthate. The… Multi-dose vialA multi-dose vial holds more than one dose and is made to be entered more than once. CDC says that once… Injection site rotationInjection site rotation means moving each injection to a different spot instead of using the same patch of… Concentration (mg/mL)Concentration is how much drug is in each unit of volume, usually written as mg/mL, mcg/mL or units/mL. It…

Frequently asked questions

Where does the Depo-Testosterone label say to inject?+
Deep in the gluteal muscle. The label says it is for intramuscular use only and should not be given intravenously.
Is all testosterone given IM?+
No. Depo-Testosterone is labeled for intramuscular use, while Xyosted is labeled for subcutaneous injection in the abdomen. Check the label of the product you use.
Why log milligrams instead of milliliters?+
Because the same volume holds a different dose at a different strength. 0.5 mL is 100 mg at 200 mg/mL but only 50 mg at 100 mg/mL.

Sources

  1. Depo-Testosterone (testosterone cypionate) US label, DailyMed
  2. Xyosted (testosterone enanthate) US prescribing information, DailyMed

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