Can you provide more info on what types of income you have?
Without knowing what type of income you have, one scenario could be that you are self-employed and took a self-employed health insurance deduction which lowered your taxable income but does not affect your self-employment taxes. This would leave you paying the 15.3% SE taxes on the amount of health insurance you deducted. So if you deducted $12,000 in insurance premiums, that would still leave you with $1,836 in SE taxes.
If you are not self-employed, then please respond with what types of income you have and a little more detail.