UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the

Securities Exchange Act of 1934

November 21, 2012

Date of Report (date of earliest event reported)

SCHIFF NUTRITION INTERNATIONAL, INC.

(Exact name of Registrant as specified in its charter)

(801) 975-5000

(Registrant’s telephone number, including area code)

Not Applicable

(Former name or former, address, if changed since last report)

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 (see General Instruction A.2. below):

Item 1.01 Entry into a Material Definitive Agreement.

Agreement and Plan of Merger with Reckitt Benckiser

On November 21, 2012, Schiff Nutrition International, Inc., a Delaware corporation (the “Company”), entered into an Agreement and Plan of Merger (the “Reckitt Merger Agreement”) with Reckitt Benckiser LLC, a Delaware limited liability company (“Parent”), Ascot Acquisition Corp., a Delaware corporation and a wholly-owned subsidiary of Parent (“Merger Sub”) and Reckitt Benckiser Group plc, a public limited company organized under the laws of England and Wales, with respect to Parent’s proposed acquisition of the Company at a price per common share of $42 in cash. A copy of the Reckitt Merger Agreement is attached hereto as Exhibit 2.1 and is incorporated into this report by reference.

Item 1.02 Termination of a Material Definitive Agreement.

Termination of Agreement and Plan of Merger with Bayer HealthCare

On November 21, 2012, the Agreement and Plan of Merger, dated October 29, 2012 (the “Bayer Merger Agreement”), by and among the Company, Bayer HealthCare LLC (“Bayer”) and Willow Road Company was terminated by the Company pursuant to Section 7.1(e) of the Bayer Merger Agreement. Concurrently with the termination of the Bayer Merger Agreement, the Company paid to Bayer a termination fee of $22 million pursuant to Section 7.2(b) of the Bayer Merger Agreement.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Forward-Looking Statements

Certain statements either contained in or incorporated by reference into this document, other than purely historical information, including estimates, projections and statements relating to the Company’s business plans, objectives and expected operating results, and the assumptions upon which those statements are based, are “forward-looking statements.” These forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions, and include words such as “believes,” “plans,” “anticipates,” “projects,” “estimates,” “expects,” “intends,” “strategy,” “future,” “opportunity,” “may,” “will,” “should,” “could,” “potential,” or similar expressions. Such forward-looking statements include the ability of the Company, Parent and Merger Sub to complete the transactions contemplated by the Reckitt Merger Agreement, including the parties’ ability to satisfy the conditions to the consummation of the tender offer and the possibility of any termination of the Reckitt Merger Agreement. The forward-looking statements contained herein are based on current expectations and assumptions that are subject to risks and uncertainties which may cause actual results to differ materially from the forward-looking statements. Actual results may differ materially from current expectations because of risks associated with uncertainties as to the timing and completion of the tender offer by

Merger Sub; the possibility that various conditions to the consummation of the tender offer by Merger Sub may not be satisfied or waived, including that a governmental entity may prohibit, delay or refuse to grant approval for the consummation of the tender offer by Merger Sub; the effects of disruption from the transactions on the Company’s business and the fact that the announcement and pendency of the transactions may make it more difficult to establish or maintain relationships with employees, suppliers and other business partners; the risk that stockholder litigation in connection with the transactions may result in significant costs of defense, indemnification and liability and potential delay; other risks and uncertainties pertaining to the business of the Company, including dependence on sales of Move Free, MegaRed and Airborne products, dependence on individual customers, adverse publicity or consumer perception regarding the Company’s nutritional supplements and/or their ingredients, similar products distributed by other companies or the nutritional supplement industry generally, the impact of competitive products and pricing pressure (including expansion of private label products), the inability to successfully bid on new and existing private label business and the impact of raw material pricing, availability and quality (particularly relating to joint care products and ingredients from third-party suppliers outside the United States, including China); claims that the Company’s products infringe the intellectual property rights of others; the inability to enforce or protect intellectual property rights and proprietary techniques against infringement; the inability to successfully launch and maintain sales outside of the United States while maintaining the integrity of the products sold and complying with local regulations; the inability to appropriately respond to changing consumer preferences and demand for new products; the inability to gain or maintain market distribution for new products or product enhancements; litigation and government or administrative regulatory action in the United States and internationally, including FDA enforcement and product liability claims; the inability or increased cost to obtain sufficient levels of product liability and general insurance; the inability to comply with existing or new regulations, both in the United States and abroad, and adverse actions regarding product formulation, claims or advertising; product recalls or a significant amount of product returns; dependence on a single manufacturing facility and potential disruptions of the Company’s manufacturing operations; the inability to maintain or attract key personnel; interruptions to the Company’s information technology systems; control by the Company’s principal stockholders; and other risks detailed in the Company’s public filings with the U.S. Securities and Exchange Commission (“SEC”) from time to time, including the Company’s most recent Annual Report on Form 10-K for the year ended May 31, 2012 and Quarterly Reports on Form 10-Q. The reader is cautioned not to unduly rely on these forward-looking statements. The Company expressly disclaims any intent or obligation to update or revise publicly these forward-looking statements except as required by law.

Important Information

This communication is neither an offer to purchase nor the solicitation of an offer to sell any securities. The Company intends to file with the SEC a solicitation/recommendation statement on Schedule 14d-9 with respect to the tender offer commenced by Merger Sub no later than November 27, 2012. Investors and security holders are urged to read the solicitation/recommendation statement and all relevant documents that are filed with the SEC in connection with the tender offer, as they become available, because they will contain important information.

Investors may obtain a free copy of all materials referenced above (when they are available) and other documents filed by the Company with the SEC at the SEC’s website at www.sec.gov and on the Company’s website at www.schiffnutrition.com.

SIGNATURES

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

Date: November 21, 2012

EXHIBIT INDEX

5