Yes your hematologist can request a serum vitamin D. For most of us, 1000 ius is not enough. You have to take into account the season and how much sun exposure you get. It is best to check it to see where you are at. In general, 1000 ius will raise your serum levels about 10 points. And it must be D3, not the D2.
John takes 5000 ius as do I. But it's best to get it checked. Optimal is around 45 -50. Last I checked, I was at 48 but John was in the 30's which is considered normal but not optimal. For the longest time, he did not get any sun. John also weighs a bit more than me so he should really be taking more. You can check out the vitamin D council here :
http://www.vitamindcouncil.org/
Ask him to check you for H-Pylorie bacteria also. This is good to check for at least once. This is the bacteria that causes ulcers and it has been associated with blood disorders also. For the first test, they can draw blood and look for anti-bodies. If positive, and they treat, subsequent testing is done via a breath test because you will always have the anti-bodies in your blood. At least that's how I understand it. If I come across the study on this I'll post it.