Tail vein

Please read the general principles of blood sampling page before attempting any blood sampling procedure.


Tail vein sampling is suitable for a small volume of blood (less than 0.2 ml) by incision (with a needle or lance) of the tail vein. It is suitable for all strains but is more difficult in black or pigmented mice as their vasculature can be difficult to observe through the skin. For competent individuals, it is quick and simple to perform. View a video of the mouse tail vein sampling technique below.

This technique may require the animals to be warmed in order to dilate the blood vessel prior to taking the sample. This can be stressful and can cause dehydration due to salivation, in addition to increasing metabolic rate, which may affect experimental data depending on the parameters observed. As a result, other routes such as saphenous vein sampling should be used where possible and, in particular, where there is a need to take multiple samples. 

The lateral tail vein is usually used and 50 µl to 0.2 ml of blood can be obtained per sample depending on the size of the animal and its health status. The tail should be washed with an antimicrobial solution such as diluted chlorohexidine to disinfect the area and to see the blood vessel. This is particularly useful for black and pigmented mice. Illumination devices can be used to improve tail vein visualisation, if necessary. 

To avoid bruising and damage to the tail, normally no more than two blood samples should be taken in any one 24-hour period. If multiple samples are required in one day (e.g. when performing a glucose tolerance test), the scab or clot may be gently soaked and removed. Where it is necessary and justifiable to take more than four samples, the use of temporary or surgical cannulation methods should be considered. The number of attempts to take a blood sample should be minimised (no more than three needle sticks in any one attempt) and sufficient time should be given for the tail to recover between blood sampling sessions. Alternate sides of the tail should be used and successive needle punctures moved towards the tail base.

If it is necessary to warm the animal, a warming cabinet should be used (no more than body temperature for up to 10 minutes) following best practice. Male mice may need to be warmed singly to avoid fighting.   

Mouse tail vein trimmed copyright NC3Rs from NC3Rs on Vimeo.

The lateral tail vein is usually accessed approximately one-third along the length of the tail from the tail tip, moving towards the base of the tail for multiple samples. Aseptic technique should be used. Animals need to be restrained which can cause stress and therefore the duration of restraint should be minimised.  

Blood flow should be stopped by applying finger pressure on the soft tissue. A finger should be placed at the blood sampling site for approximately 30 seconds before the animal is returned to its cage, and the animal monitored for adverse effects.


Number of samples One or two blood samples can be taken per session and in any 24-hour period, depending on sample volume.
Sample volume 50 ul to 0.2 ml
Equipment 25G  needle or lance
Staff resource One person is required to take the blood sample if a restraint tube is used. For large groups of animals, more staff members are required. Restraint is not required for samples in well habituated animals.
Adverse effects
  • Infection <1%
  • Haemorrhage <1%

Mice may be warmed, to dilate the blood vessel. Care should be taken to avoid hyperthermia and dehydration.

Resources and references

Tail vein sampling technique in other animals

Click here for information on tail vein blood sampling in the rat

All blood sampling techniques in the mouse

Click here for information on blood vessel cannulation in the mouse Click here for information on tail snip blood sampling in the mouse Click here for information on tail vessel microsampling in the mouse Click here for information on saphenous vein blood sampling in the mouse Click here for information on retro-orbital blood sampling techniques in the mouse Click here for information on abdominal/thoracic blood vessel blood sampling in the mouse Click here for information on cardiac puncture blood sampling in the mouse Click here for information on schedule 1 stunning followed by decapitation in the mouse Click here for information on decapitation blood sampling techniques in the mouse