How long has it been since you filed? Normally it can take up to 21 days to process an efiled return, but can take longer if the return requires more evaluation by the IRS. Here are some things you should check:
If you efiled, double-check to be sure the return was efiled successfully and accepted.
If you used Online TurboTax, you can sign into your Online Account and check the efile status at the Tax Home. If you used desktop software, you can check from within the software.
If that showed it was accepted, (or if you mailed a paper return), you can use the "Where's My Refund" tool at the IRS website below to monitor the status of your Federal refund.
https://www.irs.gov/wheres-my-refund
See what is displayed there about your refund. Is there any message?
Here are some tips when using the IRS "Where's My Refund" tool:
If the IRS WMR tool is not finding your information, you can also try phoning the IRS refund hotline. I've seen it work for some users when the WMR tool didn't. 800-829-1954