TANDEM DIABETES CARE INC

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-K

For the fiscal year ended December 31, 2025

or

For the transition period from to

Commission File Number 001-36189

Tandem Diabetes Care, Inc.

(Exact name of registrant as specified in its charter)

(858)366-6900

Registrant’s telephone number, including area code

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

__None

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☒ No ☐

Indicate by check if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes ☐No ☒

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports) and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or emerging growth company. See definitions of “large accelerated filer, “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☒

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements.☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to § 240.10D-1(b). ☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes☐ No☒

As of June 30, 2025, the last business day of the registrant’s most recently completed second fiscal quarter, the aggregate market value of the registrant’s common stock held by non-affiliates was approximately $1.3 billion based on the closing price for the common stock of $18.64 on that date. Shares of common stock held by each executive officer, director, and their affiliated stockholders have been excluded from this calculation as such persons may be deemed to be affiliates. This determination of affiliate status is not necessarily a conclusive determination for other purposes.

As of February 16, 2026, there were 68,325,927 shares of the registrant’s common stock outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive Proxy Statement on Schedule 14A for the 2026 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission not later than 120 days after the end of the fiscal year covered by this Form 10-K, are incorporated by reference in Part III, Items 10-14 of this Form 10-K.

TABLE OF CONTENTS

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K for the fiscal year ended December 31, 2025, or this Annual Report, contains “forward-looking statements” within the meaning of the federal securities laws, which statements are subject to considerable risks and uncertainties. These forward-looking statements are intended to qualify for the safe harbor from liability established by the Private Securities Litigation Reform Act of 1995. All statements included or incorporated by reference in this Annual Report, other than statements of historical fact, are forward-looking statements. You can identify forward-looking statements by the use of words such as “may,” “will,” “could,” “anticipate,” “expect,” “intend,” “believe,” “continue” or the negative of such terms, or other comparable terminology. Forward-looking statements also include the assumptions underlying or relating to such statements. In particular, forward-looking statements contained in this Annual Report may relate to, among other things, our future or assumed financial condition, results of operations, liquidity, trends impacting our financial results, the impact of our foreign currency forward hedging contracts, including business forecasts and plans, research and product development plans, manufacturing plans, strategic plans and objectives, capital needs and financing plans, product launches, geographic expansion, distribution plans, production capacity, clinical trials, regulatory approvals, competitive position and the impact of changes in the competitive environment, supply chain, and the business of our contract manufacturers and suppliers, integration of acquisitions and partner technologies, cybersecurity threats, macroeconomic pressures or uncertainties and the application of accounting guidance. We caution you that the foregoing list may not include all of the forward-looking statements made in this Annual Report. In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this Annual Report on Form 10-K, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements.

Our forward-looking statements are based on our management’s current assumptions and expectations about future events and trends, which affect or may affect our business, strategy, operations or financial performance. Although we believe that these forward-looking statements are based upon reasonable assumptions, they are subject to numerous known and unknown risks and uncertainties and are made in light of information currently available to us. Our actual financial condition and results could differ materially from those anticipated in these forward-looking statements as a result of various factors, including those set forth below under the caption “Risk Factors” in Part I, Item 1A and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in Part II, Item 7, and elsewhere in this Annual Report, as well as in the other reports we file with the Securities and Exchange Commission, or the SEC. You should read this Annual Report with the understanding that our actual future results may be materially different from and worse than what we expect.

Moreover, we operate in an evolving environment. New risk factors and uncertainties emerge from time to time and it is not possible for our management to predict all risk factors and uncertainties, nor can we assess the impact of all factors on our business or the extent to which any factor, or combination of factors, may cause actual results to differ materially from those contained in any forward-looking statements.

Forward-looking statements speak only as of the date they were made, and, except to the extent required by law or the rules of the Nasdaq Stock Market, we undertake no obligation to update or review any forward-looking statement because of new information, future events or other factors.

We qualify all of our forward-looking statements by these cautionary statements.

Risk Factor Summary

Below is a summary of material factors that make an investment in our securities speculative or risky. Importantly, this summary does not address all of the risks that we face. Additional discussion of the risks summarized in this risk factor summary, as well as other risks that we face, can be found below, under the heading “Risk Factors” in Part I, Item 1A of this Annual Report, and should be carefully considered, together with other information in this Annual Report, before making investment decisions regarding our securities.

Risks Related to Our Business and Industry

•We have incurred significant operating losses since inception and cannot assure you that we will achieve sustained profitability.

•We currently rely on sales of insulin pump products to generate a significant portion of our sales, and any factors that negatively impact sales of these products may adversely affect our business, financial condition and operating results.

•We are implementing a multi-channel managed care strategy in the United States that impacts the pricing model for our pumps and our supplies sold through the pharmacy channel. If our pharmacy channel strategy fails to achieve its intended outcome, our growth, business, results of operations, and financial condition could be materially and adversely impacted.

•Our ability to maintain and grow our sales depends in part on retaining a high percentage of our customer base.

•Failure to secure or retain adequate coverage or reimbursement for our current and future products by third-party payors could adversely affect our business, financial condition and operating results.

•Competing products, therapeutic techniques or other technological developments and breakthroughs for the monitoring, treatment or prevention of diabetes may render our products obsolete or less desirable or reduce the size of our potential market.

•Our sales and marketing efforts depend on independent distributors who are free to market products that compete with our products. If we are unable to maintain or expand our network of independent distributors, our sales may be negatively affected.

•We are dependent on clinical investigators and clinical sites to enroll participants in our current and anticipated clinical trials and human factors studies, and the failure to successfully complete clinical trials and studies could prevent us from obtaining regulatory clearances, certifications, or approvals for or commercializing our products.

•Any concerns regarding the safety or efficacy of our products could limit sales and cause unforeseen negative effects to our business prospects and financial results.

•We depend on a limited number of third-party suppliers for certain components and products, and the loss of any of these suppliers, their inability to provide us with an adequate supply of components or products, or our inability to adequately forecast customer demand, could harm our business.

Risks Related to Our International Operations

•Commercializing our products internationally may result in a variety of risks associated with international operations that could materially adversely affect our business.

•Failure to obtain any required regulatory authorization, clearance or certification in foreign jurisdictions will prevent us from marketing our products in international markets.

Risks Related to Our Indebtedness

•Servicing Convertible Senior Notes due 2029 (the 2029 Notes) will require a significant amount of cash, and we may not have sufficient cash flow from our business to repay the 2029 Notes.

Risks Related to Our Future Financings and Financial Results

•We may need or otherwise determine to raise additional funds in the future and if we are unable to raise additional funds when necessary or desirable, we may not be able to achieve our strategic objectives.

•Our operating results may fluctuate significantly from quarter to quarter.

Risks Related to Macroeconomic Conditions and External Factors

•Uncertainty in current global economic and political conditions could adversely affect our ability to predict product demand and impact our financial results and make it more likely that our actual results could differ materially from expectations.

•Public health threats, epidemics, or pandemics could have a material adverse effect on our operations, the operations of our business partners, and the global economy as a whole.

•Because our business is global, our sales and profits may fluctuate or decline in response to changes in foreign currency exchange rates or other international risks.

Risks Related to Privacy and Security

•We are subject to stringent and evolving United States and foreign laws, regulations, and rules, contractual obligations, policies and other obligations related to data privacy and security. Our actual or perceived failure to comply with such obligations could lead to regulatory investigations or actions; litigation (including class claims) and mass arbitration demands; fines and penalties; disruptions of our business operations; reputational harm; loss of sales or profits; loss of customers; and other adverse business consequences.

•If our information technology systems or those of third parties with whom we work, our data, or our software are or were compromised, we could experience adverse consequences resulting from such compromise, including but not limited to regulatory investigations or actions; litigation; fines and penalties; disruptions of our business operations; harm to our reputation; loss of sales or profits; loss of customers; and other adverse consequences.

Risks Related to Legal and Intellectual Property

•Our ability to comprehensively protect our intellectual property and proprietary technology is uncertain.

•Patent litigation in the medical device industry is common, and we may be subject to litigation that could cause us to incur substantial costs and divert the attention of management from our business.

•We may be subject to damages resulting from claims that we, or our employees, have wrongfully used or disclosed trade secrets or other proprietary information of our competitors.

Risks Related to Our Regulatory Environment

•Our products and operations are subject to extensive governmental regulation, and failure to comply with applicable requirements could cause our business to suffer.

•New products or modifications to our existing products may require new 510(k) clearances, PMAs, CE Marks or other certifications, or may require us to cease marketing or recall the modified products until clearances, certifications or approvals are obtained.

•A recall or suspension of our products, or the discovery of serious safety issues with our products, could have a significant negative impact on us.

Other Risks

•The price of our common stock may continue to fluctuate significantly.

•We depend on the knowledge and skills of our senior management and other key employees, and if we are unable to retain and motivate them or recruit additional qualified personnel, our business may suffer.

•Our ability to use our net operating loss carryforwards and certain other tax attributes may be limited.