[11] Red blood cells are used to restore oxygen-carrying capacity in people with anaemia due to trauma or other medical problems Whenever a red blood cell transfusion is being considered for a patient, it is good practice to consider not only the haemoglobin level, but also the overall clinical context, patient preferences, and whether there are alternative treatments.

[3][4] In adults, blood transfusion is typically recommended when hemoglobin levels are below 70 g/L (7 g/dL) in those who have stable vital signs, unless they have anemia due to a haematinic deficiency.

[20] A review established that in patients undergoing heart surgery a restrictive transfusion strategy of 70 to 80 g/L (7 to 8 g/dL) is safe and decreased red cell use by 24%.

[22][21][23] Guidelines recommend a higher threshold for people with heart disease of 80 g/L (8 g/dL) if they are not undergoing cardiac surgery.

[24][25] There is insufficient evidence to suggest how to manage anemia in people with blood cancers in terms of transfusion thresholds.

[26] People with thalassaemia who are transfusion dependent require a higher hemoglobin threshold to suppress their own red cell production.

Unlike the ABO antigens, a recipient will not usually react to the first incompatible transfusion because the adaptive immune system does not immediately recognize it.

[citation needed] Because this testing can take time, doctors will sometimes order a unit of blood transfused before it can be completed if the recipient is in critical condition.

[32] A potentially fatal reaction is possible if the recipient has pre-existing antibodies, and uncross matched blood is only used in dire circumstances.

The purpose of the additive solution is to maintain adequate viscosity, provide nutrients and ATP/GTP building blocks and reduce haemolysis generation throughout blood bank storage.

Usually, shelf life is limited to 4 to 6 weeks, provided that the red blood cell concentrates are stored in adequate conditions (2-6 °C).

Leucocyte depletion is most commonly performed as an integrated processing step, as bedside filtration is considered a less efficient method.

[38] These may be harmful for patients who have an impaired, reduced or not yet fully developed immune system, or if the blood donor and recipient are closely related.

Although efficient in reducing the risk of transfusion reactions including fatal transfusion-associated graft-versus-host disease (TA-GvHD), irradiation is damaging to the red blood cell membrane, which can be seen as increased levels of haemolysis during storage.

Therefore, irradiation of red blood cell concentrates is commonly only performed on demand or for specific parts of the supply.

[41][42][43] Red blood cell concentrates still contain a small amount of plasma after standard processing (usually 10-15 mL).

With a controlled, standardised freezing and thawing process, the red blood cells can be stored in frozen condition for up to 30 years.

Using an automated device allows for standardised processing to ensure optimal protection from ice crystal formation, which otherwise could damage the red blood cells.

The high-glycerol method uses 40% weight/volume glycerol, a slow freezing rate (1–3 °C per minute) and allows storage of the frozen red blood cells in common mechanical −60–80 °C freezers.

Because of the extreme storage temperature, the low-glycerol method is not compatible with the PVC tubes of blood bags.

PVC tubes are essential for sterile docking; a technology which maintains a closed system after thawing and, thereby, allows a longer post-thawing shelf-life.

[49][50] Pathogen reduction is a technology predominantly used to reduce the risk of transfusion-transmitted infectious diseases and bacterial contamination.

The modification can also be red blood cells for intrauterine transfusion where, in short, the additive solution is removed, which increases the haematocrit to between 0.70 – 0.85.

Adverse events related to transfusion in general may include allergic reactions such as anaphylaxis, infection, volume overload, and lung injury.

[58] For patients with a previous transfusion reaction history, the risk of repeated adverse events can be mitigated by choosing the proper processing modification and/or red blood cell phenotype combination.