I found out the hard way--I had some dysfunctional uterine bleeding (wouldn't stop, very heavy) and became short of breath. My gynecologist recommeded I go to the local emergency room as I was out of town on a trip. There my hemoglobin came back as 9.6--just a little lower than my previous 10.1, not transfusion time. They gave me saline, did an exam for problems, and finding none, discharged me. When I got home I was still extrememely short of breath--cooking pancakes and loading the dishwasher wiped me out for the rest of the day. I called my hematologist's office to let them know what happened. They had me go get my H&H checked that day--my hemoglobin was actually 7.3! I had lost about 3.5 grams of hemoglobin. The initial Hgb was "contracted" in my body's attempt to compensate, but as I was hydrated, the true hgb was reflected. It didn't make since for me to be short of breath at 9.6--because it wasn't a "real" number. I hope this helps someone else. By the way, as a preventative due to my history & family history, I am scheduled for a hysterectomy later this month. I have my three sons, and my hands are joyfully full!