Four supply levels are distinguished. Depending on supply levels, more or fewer blood donors with the blood type in question will be invited to donate.
The blood supply is greater than 9 days. Fewer donors invited to donate.
The blood supply is between 5 and 9 days. Normal number of donors invited.
The blood supply is running low and has dropped below 5 days. Extra donors invited.
The blood supply has dropped below 3 days. Extra donors invited in the short term.
For blood types B- and AB, limits are one day higher than mentioned above.
Due to variations in the required number of packed red cells for patients or in donor attendance, for example due to holidays, Sanquin's supply is constantly in flux. The goal is to keep the top of the bars in the chart in the green zone.