Y_Y I had almost the exact same experience a little while ago.I was getting a blood test done and I knew that I had to pull my sleeve up so I tried covering my self-harm scars with foundation which didn't seem to help much.As the nurse was taking the blood out I could see her glance at my scars every now and then,it looked like she wanted to ask but luckily she didn't.My mum wasn't too far from me so she saw the scars on my arm.Later when I got home she asked me what was on my arm.>__< And I swear I was shaking so much and sweating.I simply told her they were scratches and she seemed to believe meXD.Funny thing is they looked like cuts from a knife and clearly looked like self-harm,but she didn't seem to catch on.
:/ I have another blood test soon,if it's a different nurse who knows what'll happen.