Grace, Hello, I had a really specific blood volume test done because my dr. told me that there weren't any accurate blood volume tests available. I researched the methods and found this one that is very accurate. They offer it at select hospitals...there is more info about the test and places that offer it if you're interested. http://www.daxor.com/bva100.asp The BVA-100 is a semi-automated Blood Volume Analyzer used in conjunction with a single-use diagnostic kit. It is the first instrument to provide rapid direct measurement of a patient's blood volume. Blood volume measurements have been available for almost 60 years. The test often required 4 to 8 hours to perform and was very difficult to perform accurately. Because of this, blood volume measurements were rarely obtained. Physicians have been forced to rely on "surrogate" or substitute tests , such as hemoglobin or hematocrit which only measures the thickness of blood. Such tests can be highly misleading in many surgical and medical situations. The BVA-100 can measure blood volume in approximately 1.5 hours. In an emergency, preliminary results can be obtained within half an hour. In addition to accurately measuring a patients blood volume, the BVA-100 also determines each individual patients normal blood volume and compares the measured volume to that patients norm. For the first time, physicians have access to technology which enables them to obtain blood volume measurement rapidly and with a high degree of precision. Blood volume measurements can be instrumental in diagnosing and determining appropriate treatment for a number of acute and chronic medical conditions. If you have any questions about it please feel free to contact me. Take care, Lisa