Where do I look on my tax return to see if I included health care insurance deduction

If you have health insurance through work, generally there is no deduction for that since most employer provided health insurance is pre-tax.

And if it is deductible it would be on Schedule A line 1.  But you can only deduct medical amount that is over 7.5% of your AGI and then all your deductions have to be more than the Standard Deduction to give you any benefit.

For 2018 the standard deduction amounts are:
Single 12,000 + 1,600 for 65 and over or blind
HOH 18,000 + 1,600 for 65 and over or blind
Joint 24,000+ 1,300 for each 65 and over or blind
Married filing Separate 12,000 + 1,300 for 65 and over or blind

if you didn't report the amount you can deduct, you would have to file an amended return to get back any reduction in taxes.