If I have additional medical expenses for a specific period of time, can I deduct that from my income and then give maaser? thank you

Shalom, First of all let me send you blessings for only good health - may you and all Am Yisrael benefit from good health of body and soul. The deduction of medical expenses from one's profits before calculating the 10% ma'aser is generally not acceptable. Though there is an opinion that all household expenses may be deducted from one's income before working out the ma'aser (and medical expenses would be included in this), this view is not widely accepted as halacha. Therefore, unless there is a pressing financial need, one should calculate the 10% without deducting medical expenses. By the way, Rav Shlomo Zalman Auerbach zt"l is of the opinion that medical insurance payments may be deducted from one's income before the ma'aser is calculated. But even here many Rabbis disagree (see Hilchot Ma'aser Kesafim, Rav Yisrael Bronstein, 13,23). Blessings