It also happens when you itemize your deductions.  Health insurance is already included in taxable income thru way of itemized deductions.  So to deduct it again is of course idiotic.  I have just been adjusting the amount on line 15 of schedule 1. 

Adjust to 0 if self employed deduction is used to already reduce taxable income.  I only deducted it to the excess of allowed medical deductions over the limit for those over 65 with enough to itemize.  Because that is the only tax benefit amount gained.