| Schedule of Equity |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Three Months Ended June 30, | | Common Stock | Other
Paid-In
Capital | Retained
Earnings | Accumulated
Other
Comprehensive
Loss | Treasury Stock | Non-
controlling
Interests | Total | | ($ and shares in millions except per share amounts) | Shares | Par Value | Shares | Cost | Balance at April 1, 2025 | 3,577 | | $ | 1,788 | | $ | 44,816 | | $ | 66,097 | | $ | (4,965) | | 1,061 | | $ | (59,401) | | $ | 65 | | $ | 48,400 | | Net income attributable to Merck & Co., Inc. | — | | — | | — | | 4,427 | | — | | — | | — | | — | | 4,427 | | | Other comprehensive loss, net of taxes | — | | — | | — | | — | | (456) | | — | | — | | — | | (456) | | Cash dividends declared on common stock ($0.81 per share) | — | | — | | — | | (2,047) | | — | | — | | — | | — | | (2,047) | | | Treasury stock shares purchased | — | | — | | — | | — | | — | | 17 | | (1,345) | | — | | (1,345) | | | Share-based compensation plans and other | — | | — | | (172) | | — | | — | | (4) | | 251 | | 1 | | 80 | | | Net income attributable to noncontrolling interests | — | | — | | — | | — | | — | | — | | — | | 1 | | 1 | | | | | | | | | | | | | Balance at June 30, 2025 | 3,577 | | $ | 1,788 | | $ | 44,644 | | $ | 68,477 | | $ | (5,421) | | 1,074 | | $ | (60,495) | | $ | 67 | | $ | 49,060 | | Balance at April 1, 2026 | 3,577 | | $ | 1,788 | | $ | 45,176 | | $ | 66,721 | | $ | (4,060) | | 1,107 | | $ | (63,747) | | $ | 53 | | $ | 45,931 | | Net loss attributable to Merck & Co., Inc. | — | | — | | — | | (1,335) | | — | | — | | — | | — | | (1,335) | | Other comprehensive income, net of taxes | — | | — | | — | | — | | 118 | | — | | — | | — | | 118 | | Cash dividends declared on common stock ($0.85 per share) | — | | — | | — | | (2,117) | | — | | — | | — | | — | | (2,117) | | | Treasury stock shares purchased | — | | — | | — | | — | | — | | 6 | | (712) | | — | | (712) | | | Share-based compensation plans and other | — | | — | | (226) | | — | | — | | (5) | | 327 | | — | | 101 | | Net loss attributable to noncontrolling interests | — | | — | | — | | — | | — | | — | | — | | (2) | | (2) | | | | | | | | | | | | | Balance at June 30, 2026 | 3,577 | | $ | 1,788 | | $ | 44,950 | | $ | 63,269 | | $ | (3,942) | | 1,108 | | $ | (64,132) | | $ | 51 | | $ | 41,984 | |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Six Months Ended June 30, | | Common Stock | Other
Paid-In
Capital | Retained
Earnings | Accumulated
Other
Comprehensive
Loss | Treasury Stock | Non-
controlling
Interests | Total | | ($ and shares in millions except per share amounts) | Shares | Par Value | Shares | Cost | Balance at January 1, 2025 | 3,577 | | $ | 1,788 | | $ | 44,704 | | $ | 63,069 | | $ | (4,945) | | 1,049 | | $ | (58,303) | | $ | 59 | | $ | 46,372 | | Net income attributable to Merck & Co., Inc. | — | | — | | — | | 9,506 | | — | | — | | — | | — | | 9,506 | | | Other comprehensive loss, net of taxes | — | | — | | — | | — | | (476) | | — | | — | | — | | (476) | | Cash dividends declared on common stock ($1.62 per share) | — | | — | | — | | (4,098) | | — | | — | | — | | — | | (4,098) | | | Treasury stock shares purchased | — | | — | | — | | — | | — | | 29 | | (2,509) | | — | | (2,509) | | | Share-based compensation plans and other | — | | — | | (60) | | — | | — | | (4) | | 317 | | — | | 257 | | | Net income attributable to noncontrolling interests | — | | — | | — | | — | | — | | — | | — | | 8 | | 8 | | | | | | | | | | | | | Balance at June 30, 2025 | 3,577 | | $ | 1,788 | | $ | 44,644 | | $ | 68,477 | | $ | (5,421) | | 1,074 | | $ | (60,495) | | $ | 67 | | $ | 49,060 | | Balance at January 1, 2026 | 3,577 | | $ | 1,788 | | $ | 45,029 | | $ | 73,075 | | $ | (4,287) | | 1,102 | | $ | (62,999) | | $ | 56 | | $ | 52,662 | | | Net loss attributable to Merck & Co., Inc. | — | | — | | — | | (5,575) | | — | | — | | — | | — | | (5,575) | | | Other comprehensive income, net of taxes | — | | — | | — | | — | | 345 | | — | | — | | — | | 345 | | Cash dividends declared on common stock ($1.70 per share) | — | | — | | — | | (4,231) | | — | | — | | — | | — | | (4,231) | | | Treasury stock shares purchased | — | | — | | — | | — | | — | | 14 | | (1,637) | | — | | (1,637) | | | Share-based compensation plans and other | — | | — | | (79) | | — | | — | | (8) | | 504 | | — | | 425 | | | Net loss attributable to noncontrolling interests | — | | — | | — | | — | | — | | — | | — | | (5) | | (5) | | | | | | | | | | | | | Balance at June 30, 2026 | 3,577 | | $ | 1,788 | | $ | 44,950 | | $ | 63,269 | | $ | (3,942) | | 1,108 | | $ | (64,132) | | $ | 51 | | $ | 41,984 | |
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