HI, thanks for using healthcare magic
There are different types of anemia and by looking at the full blood count your doctor would be able to classify the type and probable causes.
Prolonged or excessive menstrual bleeding
is a common cause of iron deficiency anemia
in women. As your doctor stated , a cycle is considered short if it is less than 21 days and long if greater than 35. The duration is also ok at 6 days.
Some women can have a period that is within the normal range in terms of the number of days it lasts but the bleeding can be excessive.
The nature of the period can change during the perimenopausal time.
If your doctor believes that excessive period bleeding may be contributing to your anemia, an ultrasound
may be suggested.
I hope this helps