Can blood transfusion causer lower creatinine level?

Not much: As kidneys get sick or recover, creatinine can fluctuate up to 1.0 per day. A massive transfusion as during rough surgery or hemorrhage might result in one's labs returning to the healthy values of the donors. A clinical correlation is required.

Creatinine lowering: Yes, patients who need blood transfusion has a low volume in their intravascular (i) space. This causes an elevation of creatinine (c). When the blood is transfused and the i volume increases, the c will fall. It is similar to what happens to the c when a patient is dehydrated and is given fluid.