Blood Group Guide is a quick, offline reference for ABO and RhD blood group compatibility. It shows who can give red cells or plasma to whom, and lets you keep your own blood group and donation dates on your phone.

It is for blood donors who want to know who they can help, patients and families looking for a matching donor, students learning the basics, and volunteers running donation camps.

Check: pick a group to see who it can give to and get from. Chart: all eight groups at a glance. Learn: short explanations. Me: save your group and see when you can donate again. The Blood / Plasma switch at the top changes between red cells and plasma.

Nothing you enter leaves this phone. The app has no internet access, no accounts and no ads.

Your red cells may carry an A antigen, a B antigen, both (AB) or neither (O). A separate antigen called RhD decides plus or minus: if you have it you are positive, if not you are negative.

Your plasma naturally carries antibodies against the A or B antigens you do not have. That is why a wrong transfusion can be dangerous.

For red cells, the donor's cells must not carry an antigen the patient lacks. So O negative can give red cells to everyone, and AB positive can receive red cells from everyone.

For plasma it flips. The donor's plasma must not carry antibodies against the patient's cells. So AB plasma suits every ABO group, and group O patients can receive plasma from any ABO group. RhD does not matter for plasma.

Only a small share of people in India, roughly 5 in 100, are Rh negative. Rh negative patients should normally get Rh negative red cells. This matters most for girls and women who may become pregnant, because exposure to RhD can affect future pregnancies.

A rare type first described in Mumbai in 1952. These people lack the H antigen and often test as group O on routine checks. They can only receive blood from other Bombay group donors. It is estimated at around 1 in 10,000 people in India, and is much rarer elsewhere.

If you have been told you are Bombay group, note it on your Me page and keep your donor card with you.

Whole blood is usually given as the same ABO and RhD group. For platelets, the same ABO group is preferred, but hospitals decide case by case. This app covers red cells and plasma only.

Under the national blood donor guidelines (NBTC, 2017), a donor should generally be 18 to 65 years old (first-time donors up to 60), weigh at least 45 kg, have haemoglobin of at least 12.5 g/dL, and be in good health on the day.

The gap between two whole blood donations is at least 90 days for men and 120 days for women. The blood bank checks all of this before you donate.

Every transfusion is cross-matched in a lab before it is given. Use this app to learn and to plan donations, not to make medical decisions.