and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the Exchange Act), or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

The filing describes a stockholder-approved amendment to the long-term incentive plan, not a management change.

Material Modification to Rights of Security Holders. On May 20, 2026, at the 2026 Annual Meeting of Stockholders (the Annual Meeting) of Tandem Diabetes Care, Inc. (the Company), upon recommendation of the Company’s Board of Directors (the Board), the Company’s stockholders approved amendments to the Company’s Amended and Restated Certificate of Incorporation to: (i) provide for removal of directors with or without cause, as required by Section 141(k) of the Delaware General Corporation Law (…

Executive Vice President and Chief Commercial Officer — Mark Novara: Mr. Novara's employment was terminated without cause.

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Creation of a Direct Financial Obligation or an Obligation under an Off-Balance Sheet Arrangement of a Registrant. The information set forth under

Unregistered Sale of Equity Securities. The information set forth under

Other Events. Press Releases On February 23, 2026, the Company issued a press release announcing the proposed Offering. A copy of the press release is attached hereto as Exhibit 99.1 and incorporated herein by reference. On February 25, 2026, the Company issued a press release announcing the pricing of the Notes. A copy of the press release is attached hereto as Exhibit 99.2 and is incorporated herein by reference. Forward-Looking Statements This Current Report on Form 8-K contains “forward-l…

Entry into a Material Agreement. Indenture and Notes On February 27, 2026, Tandem Diabetes Care, Inc. (the “Company”) completed its previously announced private offering (the “Offering”) of $300.0 million aggregate principal amount of 0.00% Convertible Senior Notes due 2032 (the “Notes”), including the exercise in full of the initial purchasers’ option to purchase up to an additional $35.0 million principal amount of Notes. The Notes were issued in accordance with an indenture, dated February…

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Director — Sandra Beaver: The filing discloses the appointment of a new director to the board, which is a routine governance event and not a departure of an existing executive.

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Entry into a Material Definitive Agreement. On May 21, 2025 (the “Effective Date”), Tandem Diabetes Care, Inc. (the “Company”), Tandem Diabetes Care Europe B.V. (with the Company, the “Company Entities”), F. Hoffmann-La Roche AG, Roche Diabetes Care GmbH, Roche Diabetes Care, Inc., Roche Diagnostics Operations Inc., Roche Diagnostics GmbH and Roche Diagnostics International AG (collectively, the “Roche Entities”) entered into a Settlement, Mutual Release and Cross-License Agreement (the “Sett…

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

COO — Jean-Claude Kyrillos: The filing discloses the appointment of an experienced external executive as Chief Operating Officer, which is a significant addition to the management team rather than a departure.

Entry into a Material Definitive Agreement. On May 22, 2024, Tandem Diabetes Care, Inc., a Delaware corporation (the “Company”) and Dexcom, Inc., a Delaware corporation (“Dexcom”) entered into an Amended and Restated Development Agreement to the Original Development Agreement, dated as of November 20, 2020, between the Company and Dexcom, under which the integration of the Company’s insulin pumps with Dexcom’s Continuous Glucose Monitoring (“CGM”) devices are addressed. The Amended and Restat…

The excerpt describes the stockholder approval of employee stock purchase and long-term incentive plans, which are compensatory arrangements rather than a change in management or board composition.

Entry into a Material Definitive Agreement. On May 10, 2024, Tandem Diabetes Care, Inc., a Delaware corporation (the “Company”) and Unomedical a/s, a Danish corporation and a subsidiary of the ConvaTec Group (“Unomedical”), entered into Amendment Number 1 (“Amendment 1”) to the Distributor Agreement, dated as of January 14, 2022, between the Company and Unomedical, under which Unomedical manufactures, tests, sterilizes and packs all of the infusion sets under the Company’s brands (the “Origin…

and Exhibit 99.1 hereto is being furnished and shall not be deemed “filed” for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or the Exchange Act, or otherwise subject to the liabilities of that section, nor shall they be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Unregistered Sale of Equity Securities. The information set forth under

Entry into a Material Agreement. Indenture and Notes On March 8, 2024, Tandem Diabetes Care, Inc. (the “Company”) completed its previously announced private offering (the “Offering”) of $316.25 million aggregate principal amount of 1.50% Convertible Senior Notes due 2029 (the “Notes”), including the exercise in full of the initial purchasers’ option to purchase up to an additional $41.25 million principal amount of Notes. The Notes were issued in accordance with an indenture, dated March 8, 2…