UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): August 6, 2014

ARDELYX, INC.

(Exact name of registrant as specified in its charter)

Delaware |  | 001-36485 |  | 26-1303944
(State or other jurisdiction of incorporation) |  | (Commission File Number) |  | (IRS Employer Identification Number)

34175 Ardenwood Blvd.

Fremont, CA 94555

(Address of principal executive offices, including Zip Code)

Registrant’s telephone number, including area code: (510) 745-1700

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

¨ | Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

¨ | Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

¨ | Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

¨ | Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 7.01 | Regulation FD Disclosure.

Attached hereto as Exhibit 99.1 is a corporate presentation of Ardelyx, Inc. (the “Company”) incorporated by reference herein.

The information furnished under this Item 7.01 shall not be considered “filed” under the Securities Exchange Act of 1934, as amended, nor shall it be incorporated by reference into any future filing under the Securities Act of 1933, as amended, or under the Securities Exchange Act of 1934, as amended, unless the Company expressly sets forth in such future filing that such information is to be considered “filed” or incorporated by reference therein.

Item 9.01 | Financial Statements and Exhibits.

(d) | Exhibits.

Exhibit No. |  | Description
99.1 |  | Corporate presentation of Ardelyx, Inc.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: August 6, 2014 |  |  |  | ARDELYX, INC.
|  |  |  | By: |  | /s/ Mark Kaufmann
|  |  |  |  |  | Mark Kaufmann
|  |  |  |  |  | Chief Financial Officer

EXHIBIT INDEX

Exhibit No. |  | Description
99.1 |  | Corporate presentation of Ardelyx, Inc.