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Lateral Tail Vein Injections in Mice and Rats (Preferred Technique for Vascular Access in Mice)

Description of procedure:

Only properly trained personnel will perform this procedure.
The most accessible vessels for intravenous administration in rodents are veins that run the length of both lateral aspects of the tail.

  • Sterile 28-30 gauge needles for mice
  • Sterile 25-27 gauge needles for rats
  • 300-500 microliter syringes for mice
  • 1ml or 3ml syringes for rats
  • Heating device
  • Gauze sponges
  1. Weigh each animal before injection.  Up to 1% of the animal’s body weight in volume can be administered per injection.
  2. Record body weights and agent volumes to be administered for each animal.
  3. Prior to injection, warm animals for 5-10 minutes to dilate the veins. Animals may be warmed by placing the animal in a commercially available warming box or by using a warm water circulating pad placed under the cage. These are the safest and most effective ways to warm rodents. If an overheard heat lamp is used, extra care must be taken to prevent overheating the animals.
  4. Lightly anesthetize animals and position them on their side. Animals should be placed on a rechargeable heat pack or circulating warm water pad to keep them warm during anesthesia.

Please note: With brown or black mice and rats, an additional light source may be necessary to aid in visualizing the tail veins. Rats have scales making the vein difficult to see, especially in older adults. The scales are removed by gently cleaning the tail with a warm saline or chlorhexidine solution making the veins more apparent- wipe in the direction of the scales to avoid irritation to the tail.

  1. Mouse: Grasp the tail at the distal (furthest from the animal’s body) end. The index and middle fingers of the non-dominant hand are placed around the tail above where the needle will be inserted (these fingers act as a tourniquet) and the lower part of the tail is held between the thumb and ring fingers below the injection site. Slight opposing pressure is applied with both sets of fingers to straighten and stabilize the tail. Release pressure before administering the agent into the vein.

image 1     image 2
Rats: A tourniquet is used to constrict the vein. A tourniquet is made with a rubber band wrapped around the top of the tail and held together firmly with a hemostat. The tourniquet is released before the agent is administered into the vein.
 image 3     image 4

  1. Hold the syringe with the dominant hand near the bottom so that the remaining fingers are near the plunger and can easily push the agent into the vessel without disrupting the needle in the vein.
  2. Insert the needle (small gauge, 28-30 for mice and 25-27 for rats), bevel up, into the vein towards the direction of the head. Keep the needle and syringe parallel to the tail. Slight back pressure can be used to pull blood into the syringe to confirm proper placement in the vessel before injecting. Alternately, correct placement can be confirmed by feel - the needle should advance smoothly into the vein.

Please note: With mice, elevating the animal about 4-6 inches off the table may be helpful with keeping the needle and syringe parallel to the vein.

  1. Slowly inject. If there is resistance and/or a blister-like area appears above the needle on the tail, the needle should be removed and re-inserted above the first site.
  2. Remove the needle and apply gentle compression until bleeding has stopped.
  3. Return animals to their cage and observe for 5-10 minutes to make sure that bleeding has not resumed.

Literature search words required:
Literature search was performed for refinement of this Standard Procedure on 01-28-08.

Key Words

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Years Covered

IV injections in mice/ rodents/alternatives to IV injections in rodents


Full database search to the present

IV injections in mice/ rodents/alternatives to IV injections in rodents


Full database search to the present

This procedure requires anesthesia.
All agents administered to animals should be listed in the "Agents" section of RIO.
Adverse Effects:

Procedure, Agent or Phenotype

Potential Adverse Effects


Injection into lateral tail vein

Peri-vascular irritation

Infiltrate the tail around the vessel with saline if the agent has the potential to cause tissue damage

Injection into lateral tail vein

Blood loss


Monitoring Parameters:

Monitoring Parameters


PI/Lab will Document

General appearance/activity level

Will follow monitoring intervals described in protocol


Condition of tail

Day 1 post-injection and then will follow monitoring intervals described in protocol


General appearance/activity level

Will follow monitoring intervals described in protocol


Describe the conditions, complications, and criteria (e.g. uncontrolled infection, loss of more than 15% body weight, etc.) that would lead to removal of an animal from the study, and describe how this will be accomplished (e.g. stopping treatment, euthanasia).

Animals will be euthanized if there is any evidence of tissue necrosis from peri-vascular administration.

For all investigators housing animals with tumor formation, skin lesions, neurological deficits, or that are in Category E, list the expected characteristics/clinical presentations and endpoints of the animal model and the criteria for euthanasia. Note: The IACUC also requires such lists to be posted in the respective animal rooms and monitored by the IACUC compliance staff and LARC, to assure PI adherence to the endpoints listed.