Sec Form 4 Filing - BERGER DAVID B @ TANDEM DIABETES CARE INC - 2021-05-17

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 BERGER DAVID B 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 Business/Compliance (Last) (First) (Middle) C/O TANDEM DIABETES CARE, INC., 11075 ROSELLE STREET 3. Date of Earliest Transaction (MM/DD/YY) 05/17/2021 (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 05/17/2021 A 296 ( 1 ) A $ 66.76 4,862 D Common Stock 05/18/2021 M( 2 ) 243 A $ 73.726 443 I Berger Family Trust ( 3 ) Common Stock 05/18/2021 S( 2 ) 201 D $ 89.14 242 I Berger Family Trust ( 3 )

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 ( 4 ) ( 5 ) 05/18/2021 A 2,599 ( 6 ) ( 6 ) Common Stock 2,599 $ 0 2,599 D Performance Stock Unit ( 4 ) ( 7 ) 05/18/2021 A 2,599 ( 7 ) ( 7 ) Common Stock 2,599 $ 0 2,599 D Stock Option ( 4 ) $ 81.63 05/18/2021 A 7,940 ( 8 ) ( 9 ) Common Stock 7,940 $ 0 7,940 D Warrant $ 73.726 05/18/2021 M 243 05/18/2021 ( 10 ) Common Stock 243 $ 73.726 0 I See Footnote ( 3 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other BERGER DAVID B C/O TANDEM DIABETES CARE, INC. 11075 ROSELLE STREET SAN DIEGO, CA92121 EVP, Chief Business/Compliance Signatures s/ Karrie Rexford, Attorney-in-Fact for David B. Berger 05/20/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The reporting person is voluntarily reporting the acquisition of shares of common stock pursuant to the Tandem Diabetes Care, Inc. Amended and Restated 2013 Employee Stock Purchase Plan ("ESPP"), for the ESPP purchase period of November 17, 2020 through May 17, 2021. This transaction is also exempt under Rule 16b-3(c). ( 2 )The transaction reflects the cashless exercise of warrants to purchase common stock, at an exercise price of $73.726. Pursuant to the terms of the warrant, the shares of common stock were sold at a price equal to the average of the closing prices of the shares over the 30-day period ending three days prior to the date on which the notice of exercise was received by the Issuer. ( 3 )The securities are held by the Berger Family Trust dated April 16, 2008. ( 4 )Awarded on May 18, 2021 pursuant to the Tandem Diabetes Care, Inc. 2013 Stock Incentive Plan, as amended, and the agreements related thereto (the "2013 Plan"). ( 5 )Each restricted stock unit ("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. ( 6 )RSU vest as to twenty-five percent (25%) of the total number of shares subject to the RSU on the one-year anniversary of the grant date, and the remaining shares shall vest in twelve (12) equal quarterly installments thereafter, subject to the terms of the 2013 Plan. ( 7 )Each performance stock unit ("PSU") represents a contingent right to receive one share of Tandem Diabetes Care, Inc. (the "Company") common stock based upon the achievement of certain pre-defined performance metrics as of December 31, 2024 (the "Measurement Date"). The number of shares issued may range from 0% to 200 % of the amount specified above, based upon (i) Company's actual performance relative to the pre-defined performance metrics, and (ii) subject to the awardee's continuing service through the Measurement Date. If minimum performance metrics are not met, no PSU's will vest. ( 8 )The option shall vest as to twenty-five percent (25%) of the underlying shares on the one-year anniversary of the grant date, and the remaining shares shall vest in thirty-six (36) equal monthly installments thereafter, subject to the terms of the 2013 Plan. ( 9 )The expiration date for these options is 10 years from the date of grant. ( 10 )The expiration dates for these warrants are August 31, 2021 (135 shares), July 3, 2022 (54 shares) and August 21, 2022 (54 shares).

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* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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