Losing Hair
When counting the number of hairs you lose per day you cannot be very accurate. Within 100 strands or so is good enough. There is not a lot to worry about if you are only losing about 100 strands per day. This is seen as a natural amount. New strands are expected to grow in a 12 week cycle. If you feel you are losing hair at a rate greater than this it would be wise to investigate the problem further.
If you suffer from a medical condition this could the the cause. This is true, especially it is a condition that affects your thyroid gland. Other conditions that can stunt hair growth are diabetes and lupus. Viviscal may not help in these cases.