Exhibit 3.1

CERTIFICATE OF AMENDMENT

TO THE

AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

OF

BAXTER INTERNATIONAL INC.

Baxter International Inc. (the “Corporation”), a corporation organized and existing under the General Corporation Law of the State of Delaware, hereby certifies as follows:

1. The first paragraph of Article FIFTH of the Corporation’s Amended and Restated Certificate of Incorporation is hereby amended and restated in its entirety to read as follows:

“FIFTH: The number of directors which shall constitute the whole Board of Directors of the Corporation shall be the number from time to time fixed by the Board of Directors but in no event shall be less than seven. A decrease in the number of directors shall not affect the term of office of any director then in office.”

2. The foregoing amendment was duly adopted in accordance with the provisions of Section 242 of the General Corporation Law of the State of Delaware.

IN WITNESS WHEREOF, the Corporation has caused this Certificate of Amendment to be executed and acknowledged on its behalf by its duly authorized officer as of this fifth day of May, 2026.