Sec Form 4 Filing - Gasser Elizabeth Anne @ TANDEM DIABETES CARE INC - 2022-05-27

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Gasser Elizabeth Anne 2. Issuer Name and Ticker or Trading Symbol TANDEM DIABETES CARE INC [ TNDM] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) EVP, Chief Strategy Officer (Last) (First) (Middle) C/O TANDEM DIABETES CARE, INC., 11075 ROSELLE STREET 3. Date of Earliest Transaction (MM/DD/YY) 05/27/2022 (Street) SAN DIEGO, CA92121 4. If Amendment, Date Original Filed (MM/DD/YY) 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 (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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 05/27/2022 M 373 A $ 0 1,448 D Common Stock 05/27/2022 F( 1 ) 129 D $ 70.81 1,319 D

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 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( 2 ) ( 3 ) 05/27/2022 M 373 ( 4 ) ( 4 ) Common Stock 373 $ 0 2,981 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Gasser Elizabeth Anne C/O TANDEM DIABETES CARE, INC. 11075 ROSELLE STREET SAN DIEGO, CA92121 EVP, Chief Strategy Officer Signatures s/ Rachel Malina, Attorney-in-Fact for Elizabeth A. Gasser 06/01/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Shares withheld by Tandem Diabetes Care, Inc. (the Company) to satisfy tax withholding requirements on vesting of restricted stock units (RSU). No shares were sold. ( 2 )Granted pursuant to the Tandem Diabetes Care, Inc. 2013 Stock Incentive Plan ("the 2013 Plan"). ( 3 )Each RSU represents a contingent right to receive either one share of common stock of the Issuer or cash in lieu thereof, at the Issuer's discretion, in accordance with the terms of the 2013 Plan. ( 4 )RSUs granted on 5/27/2020 vest as to twenty-five percent (25%) of the total number of shares subject to the RSU on 5/27/2021, and the remaining shares shall vest in twelve (12) equal quarterly installments thereafter.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* 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).

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