Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person * TWOMEY CHRISTOPHER J 2. Issuer Name and Ticker or Trading Symbol TANDEM DIABETES CARE INC [TNDM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 12400 HIGH BLUFF DRIVE 3. Date of Earliest Transaction (Month/Day/Year) 05/20/2026 (Street) SAN DIEGO, CA 92130 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 05/21/2026 M 8,759 A $ 0 24,434 D Common Stock 5,112 I See Footnote(1) Common Stock 7,568 I See Footnotes(2)

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Restricted Stock Unit

(3)

05/20/2026

A

10,220

(4)

(4)

Common Stock

10,220

$ 0

10,220

D

Restricted Stock Unit

(3)

05/21/2026

M

8,759

(5)

(5)

Common Stock

8,759

$ 0

0

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
TWOMEY CHRISTOPHER J 12400 HIGH BLUFF DRIVE SAN DIEGO, CA 92130	X

Signatures

/s/ Jerilyn Laskie, Attorney-in-Fact for Christopher J. Twomey		05/22/2026
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	The securities are held by the Chris J. Twomey and Rebecca J. Twomey Family Trust UTD September 20, 2002.
(2)	The securities are directly owned by Twomey Family Investments, LLC. The Reporting Person is co-manager of Twomey Family Investments, LLC and shares voting and investment power over these securities held by Twomey Family Investments, LLC and may be deemed to have indirect beneficial ownership of such shares. The Reporting Person disclaims beneficial ownership of such securities held by Twomey Family Investments, LLC, except to the extent of his proportionate pecuniary interest therein.
(3)	Each restricted stock units (RSU) represents a contingent right to receive either one share of the Issuers common stock or cash in lieu thereof, at the Issuers discretion, in accordance with the terms of the Tandem Diabetes Care, Inc. 2023 Long-Term Incentive Plan, as amended, and agreements related thereto (the 2023 Plan).
(4)	RSU will vest on the one-year anniversary of the grant date, subject to the terms of the 2023 Plan.
(5)	On May 21, 2025, the Reporting Person was granted 8,759 RSUs, all of which vested and converted into shares of the Issuers common stock on the one-year anniversary thereof in accordance with the 2023 Plan.
Remarks: Ex. 24: Power of Attorney

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