Concentration and memory

I work and when someone tells me something maybe 5-10 minutes later I'm not sure if I got it right on the instructions.
It seems as though I can't concentrate very well..What is wrong...lack of oxygen/blood in the brain or what?

[margypops]

I think possibly it could be a lack of concentration, maybe you are doing something else and not focused on what they are saying, so try focusing on the person when they talk to you, are you on any meds as they can make you have some short term memory loss. Are you anxious about anything as anxiety can also be a cause .