Household income means the total federal adjusted gross income, as defined in the Internal Revenue Code, plus (1) any Nebraska adjustments increasing the total federal adjusted gross income, (2) any interest or dividends received by the owner regarding obligations of the State of Nebraska or any political subdivision, authority, commission, or instrumentality thereof to the extent excluded in the computation of gross income for federal income tax purposes, (3) any social security or railroad retirement benefit to the extent excluded in the computation of gross income for federal income tax purposes, and (4) any carryforward of a net operating loss to the extent deducted for federal income tax purposes, of the claimant and spouse, and any additional owners who are natural persons and who occupy the homestead, for the taxable year of the claimant immediately prior to the year for which the claim for exemption is made, less all medical expenses actually incurred and paid by the claimant, his or her spouse, or any owner-occupant which are in excess of four percent of household income calculated prior to the deduction for medical expenses. For purposes of this section, medical expenses means the costs of health insurance premiums and the costs of goods and services purchased from a person licensed under the Uniform Credentialing Act or a health care facility or health care service licensed under the Health Care Facility Licensure Act for purposes of restoring or maintaining health, including insulin and prescription medicine, but not including nonprescription medicine.