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): May 12, 2017

DexCom, Inc.

(Exact Name of the Registrant as Specified in Its Charter)

(858) 200-0200

(Registrant’s Telephone Number, Including Area Code)

(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):

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Emerging growth company  ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☐

On May 12, 2017, DexCom, Inc. (“DexCom”) completed its previously announced sale of $350 million aggregate principal amount of 0.75% Convertible Senior Notes due 2022 (the “Notes”), in a private placement in reliance on Section 4(a)(2) of the Securities Act of 1933, as amended (the “Securities Act”), to the initial purchasers for initial resale to qualified institutional buyers pursuant to an exemption from registration provided by Rule 144A promulgated under the Securities Act.

The Notes were issued pursuant to an Indenture, dated as of May 12, 2017 (the “Indenture”), between DexCom and U.S. Bank National Association, as trustee (“U.S. Bank”). The Notes are senior, unsecured, obligations of DexCom. The Notes will bear interest at a rate of 0.75% per year, payable in cash semiannually in arrears on May 15 and November 15 of each year, beginning on November 15, 2017. The Notes mature on May 15, 2022 unless repurchased, redeemed or converted in accordance with their terms prior to such date.

DexCom may not redeem the Notes prior to May 15, 2020. DexCom may redeem for cash all or any portion of the Notes, at its option, on or after May 15, 2020 if certain conditions are met. No sinking fund is provided for the Notes.

The Indenture includes customary terms and covenants, including certain events of default after which the Notes may be due and payable immediately. The following events are considered “events of default,” which may result in acceleration of the maturity of the Notes:

The Notes are convertible into cash, shares of DexCom’s common stock, par value $0.001 per share (“common stock”), or a combination thereof, at DexCom’s election, at an initial conversion rate of 10.0918 shares of common stock per $1,000 principal amount of the Notes, which is equivalent to an initial conversion price of approximately $99.09 per share of common stock, subject to adjustment.

Holders of the Notes who convert their Notes in connection with a make-whole fundamental change (as defined in the Indenture) or following the delivery by DexCom of a notice of redemption are, under certain circumstances, entitled to an increase in the conversion rate.

Additionally, in the event of a fundamental change (as defined in the Indenture), holders of the Notes may require DexCom to repurchase all or a portion of their Notes at a price equal to 100% of the principal amount of Notes, plus any accrued and unpaid interest, including any additional interest, to, but excluding, the repurchase date.

Holders of the Notes may convert all or a portion of their Notes at their option prior to 5:00 p.m., New York City time, on the business day immediately preceding February 15, 2022, in multiples of $1,000 principal amount, only under the following circumstances:

On or after February 15, 2022, until 5:00 p.m., New York City time, on the business day immediately preceding the maturity date, holders of the Notes may convert all or a portion of their Notes regardless of the foregoing circumstances.

A copy of the Indenture is attached hereto as Exhibit 4.1 and is incorporated herein by reference. The description of the Notes contained in this Form 8-K is qualified in its entirety by reference to the Indenture.

The information set forth in Item 1.01 above is incorporated by reference into this Item 2.03.

The information set forth under Item 1.01 above is incorporated by reference into this Item 3.02.

(d) Exhibits.

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.

EXHIBIT INDEX