BIIB
Biogen Inc. Common Stock
stockNASDAQ
At CloseOct 30, 2026 4:06:30 PM EDT
253.60USD+1.582%(+3.95)1,303,306
Pre-marketOct 30, 2026 10:29:58 AM EDT
253.78USD+1.654%(+4.13)
As of 2026-10-15, there were 5,500,386 shares short with a short interest of 3.75%.
BIIB Short Interest - Official
BIIB Short Position Change - Official
BIIB Short Interest - Official
| Settlement Date1 | Short Interest % | Short Position | Days to Cover2 | Short Position Change | Short Position Change % | Shares Out | Shares Float |
|---|---|---|---|---|---|---|---|
| 2026-10-15 | 3.75 | 5,500,386 | 4.39 | -465,506 | -7.80 | 147,753,998 | 146,639,196 |
| 2026-09-30 | 4.07 | 5,965,892 | 4.87 | +148,095 | +2.55 | 147,753,998 | 146,431,897 |
| 2026-09-15 | 3.97 | 5,817,797 | 7.59 | +91,166 | +1.59 | 147,753,998 | 146,431,897 |
| 2026-08-31 | 3.91 | 5,726,631 | 8.66 | +536,076 | +10.33 | 147,753,998 | 146,431,897 |
| 2026-08-14 | 3.54 | 5,190,555 | 6.13 | -263,346 | -4.83 | 147,753,998 | 146,431,897 |
| 2026-07-31 | 3.72 | 5,453,901 | 4.73 | -545,232 | -9.09 | 147,753,998 | 146,431,749 |
| 2026-07-15 | 4.10 | 5,999,133 | 3.45 | +275,939 | +4.82 | 147,637,117 | 146,316,091 |
| 2026-06-30 | 3.91 | 5,723,194 | 4.14 | +534,358 | +10.30 | 147,637,117 | 146,316,091 |
| 2026-06-15 | 3.55 | 5,188,836 | 5.65 | +458,878 | +9.70 | 147,637,117 | 146,316,091 |
| 2026-05-15 | 3.23 | 4,729,958 | 4.21 | +254,488 | +5.69 | 147,637,117 | 146,588,334 |
| 2026-04-30 | 3.06 | 4,475,470 | 3.59 | +60,512 | +1.37 | 147,637,117 | 146,262,165 |
| 2026-04-15 | 3.02 | 4,414,958 | 3.07 | +588,517 | +15.38 | 146,758,528 | 146,262,165 |
| 2026-03-31 | 2.62 | 3,826,441 | 3.47 | -508,354 | -11.73 | 146,758,528 | 146,262,165 |
| 2026-03-13 | 2.96 | 4,334,795 | 5.15 | +131,883 | +3.14 | 146,758,528 | 146,262,165 |
| 2026-02-27 | 2.87 | 4,202,912 | 4.63 | -342,259 | -7.53 | 146,758,528 | 146,262,165 |
| 2026-02-13 | 3.11 | 4,545,171 | 2.45 | -147,466 | -3.14 | 146,758,528 | 146,262,165 |
| 2026-01-30 | 3.21 | 4,692,637 | 3.62 | +14,601 | +0.31 | 146,702,272 | 146,262,165 |
| 2026-01-15 | 3.20 | 4,678,036 | 2.62 | +211,699 | +4.74 | 146,702,272 | 146,262,165 |
| 2025-12-31 | 3.05 | 4,466,337 | 1.67 | -2,124,621 | -32.24 | 146,702,272 | 146,262,165 |
| 2025-12-15 | 4.51 | 6,590,958 | 3.67 | -186,515 | -2.75 | 146,702,272 | 146,262,165 |
| 2025-11-28 | 4.63 | 6,777,473 | 3.26 | +636,629 | +10.37 | 146,702,272 | 146,266,566 |
| 2025-11-14 | 4.20 | 6,140,844 | 3.19 | +496,190 | +8.79 | 146,702,272 | 146,312,044 |
Historical data is split-adjusted.
1 Data from Finra. Finra publishes an updated file every two weeks.
2 Days to Cover (DTC) is also called Short Ratio. This is the Short Position / Average Daily Trading Volume.