The test for total testosterone has been widely available for many years but is not a very reliable measure of how much testosterone is actually “free” and available to the cells. There are few reliable and affordable tests currently available for free testosterone. Another test available is for SHBG. By running a test for total testosterone and another for SHBG, your doctor can use these values to calculate the amount of free testosterone in the blood. This is done by dividing the total testosterone value by the value of the SHBG and multiplying by 100 to arrive at a percentage value called the free androgen index. In normal men, this value should stay between 70 to 100 percent, but in andropausal men, it may fall to below 50 percent. In any event, measurement of total testosterone is probably the most widely available and utilized test today. In the United States at present, it also remains the standard for indicating a need for replacement therap.y <br> <br> When to take the blood sample for these tests is important because the level of testosterone normally varies from a high point in the morning to lower points throughout the day. The blood sample should be drawn between 8:00 and 9:00 AM to be sure it will provide the highest level of testosterone during the cycle. The normal range for total testosterone is 300 – 1000 ng/dl.<br>