My lymphocyte level is .4. Is this significantly low?

What does the Doctor that asked for the tests say ? ?

It certainly falls well below the normal range you indicate. Has the Doc. who ordered the tests explained the results to you?

As per normal levels it is low. There are several possible causes of a low lymphocyte levels. Certain medications can also lower your lymphocyte count. Another common reason is viral infections, which can cause a temporary drop in lymphocytes level as more of them are drawn away to fight the infection. In this case lymphocyte count usually returns to normal within weeks after the infection is resolved. Only the doctor who ordered the tests could evaluate the condition properly, we can only make assumptions here.

It is low, yes.