For 2018 - 2020 many taxpayers that itemized in the past will find that they can no longer itemize because the standard deduction has doubled so all of their itemized deduction s no longer exceed the standard deduction.

Only if all itemized deductions exceed the standard deduction will it be of benefit.

Not all itemized deductions count the full amount. Medical expenses are reduced by 7.5% of AGI so if your AGI is $30,000, for example, then only medical expenses more than $2,250 would be an itemized deduction.

The 2018 tax law also caps the total of Sales tax OR State and local income tax, Property (real estate and personal property) taxes at $10,000.

Mortgage interest on loans after Dec 16, 2017 may be limited.

The Mortgage must be secured by the property to qualify.

Interest on home equity loans and lines of credit are deductible only if the borrowed funds are used to buy, build, or substantially improve the taxpayer’s home that secures the loan.

You can check the actual amount of itemized deductions by using the Search Topics for "itemized deductions, choosing" (under "My Account, Tools" in the online versions). Click on "Change my deduction". That will display the actual amount of itemized deductions vs. the standard deduction. (Be sure to uncheck "Change my deduction" after checking it so you do not lock in the wrong deduction.


2020 standard deductions

$12,400 Single
$18,650 Head of Household
$24,800 Married Jointly

Add an additional $1,300 for over age 65 or blind
This amount increases to $1,650 if the taxpayer is also unmarried.

Is there some reason to file separate?

If you file MFS (Married Filing Separately) keep in mind that there are several limitations to MFS.  Married filing Jointly is usually the better way to file.
 
A few of those limitations are: (see IRS Pub 17 for the full list

https://www.irs.gov/pub/irs-pdf/p17.pdf page 21

1. Your tax rate generally is higher than on a joint return.
2. Your exemption amount for figuring the alternative minimum tax is half that allowed on a joint return.
3. You cannot take the credit for child and dependent care expenses in most cases, and the amount you can exclude from income under an employer's dependent care assistance you are legally separated or living apart from your spouse, you may be able to file a separate return and still take the credit. For more information about these expenses, the credit, and the exclusion, see chapter 32.
4. You cannot take the earned income credit.
5. You cannot take the exclusion or credit for adoption expenses in most cases.
6. You cannot take the education credits (the American opportunity credit and lifetime learning credit) or the deduction for student loan interest.
7. You cannot exclude any interest income from qualified U.S. savings bonds you used for higher education expenses.
8. If you lived with your spouse at any time during the tax year:
a. You cannot claim the credit for the elderly or the disabled, and
b. You must include in income a greater percentage (up to 85%) of any social security or equivalent railroad retirement benefits you received.
9. The following credits and deductions are reduced at income levels half those for a joint return:
a. The child tax credit,
b. The retirement savings contributions credit,
10. Your capital loss deduction limit is $1,500 (instead of $3,000 on a joint return).
11. If your spouse itemizes deductions, you cannot claim the standard deduction. If you can claim the standard deduction, your basic standard deduction is half the amount allowed on a joint return.

- If you live in a community property state you must allocate community income between both spouses..
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- Community property states.   If you live in Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, or Wisconsin and file separately, your income may be considered separate income or community income for income tax purposes. See Publication 555. http://www.irs.gov/publications/p555/index.html

 
See this TurboTax article for help with this.
https://ttlc.intuit.com/questions/1894449-married-filing-jointly-vs-married-filing-separately

https://ttlc.intuit.com/questions/1901162-married-filing-separately-in-community-property-states