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Amphastar Pharmaceuticals (AMPH) Short Interest Ratio & Short Volume

Amphastar Pharmaceuticals logo
$29.19 -0.20 (-0.68%)
Closing price 04:00 PM Eastern
Extended Trading
$29.33 +0.14 (+0.48%)
As of 04:40 PM Eastern
Extended trading is trading that happens on electronic markets outside of regular trading hours. This is a fair market value extended hours price provided by Polygon.io. Learn more.

Amphastar Pharmaceuticals Short Interest Data

Amphastar Pharmaceuticals (AMPH) has a short interest of 4.13 million shares, representing 12.07% of the float (the number of shares available for trading by the public). This marks a 2.74% increase in short interest from the previous month. The short interest ratio (days to cover) is 7.6, indicating that it would take 7.6 days of the average trading volume of 617,114 shares to cover all short positions.

Current Short Interest
4,130,000 shares
Previous Short Interest
4,020,000 shares
Change Vs. Previous Month
+2.74%
Dollar Volume Sold Short
$123.20 million
Short Interest Ratio
7.6 Days to Cover
Last Record Date
August 15, 2025
Outstanding Shares
46,490,000 shares
Float Size
34,220,000 shares
Short Percent of Float
12.07%
Today's Trading Volume
553,530 shares
Average Trading Volume
617,114 shares
Today's Volume Vs. Average
90%
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AMPH Short Interest Over Time

AMPH Days to Cover Over Time

AMPH Percentage of Float Shorted Over Time

Amphastar Pharmaceuticals Short Interest History

Report DateTotal Shares Sold ShortDollar Volume Sold ShortChange from Previous ReportPercentage of Float ShortedDays to CoverPrice on Report Date
8/15/20254,130,000 shares $123.20 million +2.7%12.1%7.6 $29.83
7/31/20254,020,000 shares $84.22 million +0.3%11.8%7.6 $20.95
7/15/20254,010,000 shares $84.93 million -1.2%11.6%7.9 $21.18
6/30/20254,060,000 shares $93.22 million -0.5%11.7%7.3 $22.96
6/15/20254,080,000 shares $105.35 million -0.5%11.8%7.3 $25.82
5/31/20254,100,000 shares $106.11 million +2.2%11.8%7 $25.88
5/15/20254,010,000 shares $97.52 million +24.9%11.5%6.4 $24.32
4/30/20253,210,000 shares $78.36 million +8.1%9.2%5.1 $24.41
4/15/20252,970,000 shares $69.80 million -13.2%8.5%4.9 $23.50
3/31/20253,420,000 shares $99.15 million -11.2%9.7%5.5 $28.99
3/15/20253,850,000 shares $102.64 million -6.8%10.9%6.2 $26.66
2/28/20254,130,000 shares $117.42 million +1.5%11.6%6.9 $28.43
2/15/20254,070,000 shares $126.25 million -1.2%11.3%7.4 $31.02
1/31/20254,120,000 shares $143.66 million -10.4%11.5%7.5 $34.87
1/15/20254,600,000 shares $166.70 million -4.6%12.9%8.8 $36.24
12/31/20244,820,000 shares $178.97 million +10.3%13.5%10.1 $37.13
12/15/20244,370,000 shares $184.59 million +6.1%12.2%10.3 $42.24
11/30/20244,120,000 shares $186.18 million -2.8%11.5%11 $45.19
11/15/20244,240,000 shares $189.15 million -2.3%11.8%12 $44.61
10/31/20244,340,000 shares $219.30 million +2.6%12.2%12.6 $50.53
10/15/20244,230,000 shares $208.58 million -2.8%11.7%12 $49.31
9/30/20244,350,000 shares $211.11 million +5.3%12.0%11.9 $48.53
9/15/20244,130,000 shares $198.61 million -1.9%11.4%10.4 $48.09
8/31/20244,210,000 shares $205.20 million No Change12.0%11.2 $48.74
8/15/20244,210,000 shares $190.80 million -7.5%12.0%10.9 $45.32
7/31/20244,550,000 shares $198.02 million +7.6%12.9%11.6 $43.52
7/15/20244,230,000 shares $163.95 million +1.4%12.0%11.7 $38.76
6/30/20244,170,000 shares $166.80 million +0.5%11.9%11.5 $40.00
6/15/20244,150,000 shares $168.03 million +10.4%11.8%12.1 $40.49
5/31/20243,760,000 shares $159.16 million -0.3%10.3%10.3 $42.33
5/15/20243,770,000 shares $160.00 million -5.5%10.7%9.2 $42.44
4/30/20243,990,000 shares $164.59 million +3.1%11.4%9.7 $41.25
4/15/20243,870,000 shares $157.82 million +5.5%11.0%9 $40.78
3/31/20243,670,000 shares $161.15 million +1.9%10.6%7.8 $43.91
3/15/20243,600,000 shares $154.98 million -3.2%10.4%7.5 $43.05
2/29/20243,720,000 shares $173.24 million +3.6%10.3%7.5 $46.57
2/15/20243,590,000 shares $199.28 million +12.5%10.0%7.9 $55.51
1/31/20243,190,000 shares $170.22 million +8.5%8.9%6.6 $53.36
1/15/20242,940,000 shares $159.38 million +5.8%8.2%6.5 $54.21
12/31/20232,780,000 shares $171.94 million -1.8%7.8%6.5 $61.85
12/15/20232,830,000 shares $160.18 million -0.7%8.0%6.9 $56.60
11/30/20232,850,000 shares $160.51 million -1.4%8.0%6 $56.32
11/15/20232,890,000 shares $166.23 million +15.6%8.1%6.4 $57.52
10/31/20232,500,000 shares $113.18 million -6.0%6.9%5.7 $45.27
10/15/20232,660,000 shares $121.72 million +1.5%7.3%6.2 $45.76
9/30/20232,620,000 shares $120.49 million -2.6%7.2%5.8 $45.99
9/15/20232,690,000 shares $123.12 million +106.9%7.4%5.9 $45.77
8/31/20231,300,000 shares $69.30 million -12.8%3.6%3 $53.31
8/15/20231,490,000 shares $85.30 million +4.2%4.1%3.4 $57.25
7/31/20231,430,000 shares $86.79 million -30.9%4.0%3.2 $60.69
7/15/20232,070,000 shares $115.65 million +3.0%5.8%4.5 $55.87
6/30/20232,010,000 shares $115.51 million -3.4%5.6%4.5 $57.47
6/15/20232,080,000 shares $108.64 million +10.6%5.8%4.7 $52.23
5/31/20231,880,000 shares $83.42 million -1.1%5.3%4.7 $44.37
5/15/20231,900,000 shares $79.34 million +2.2%5.3%4.8 $41.76
4/30/20231,860,000 shares $66.53 million +29.2%5.3%5.3 $35.77
4/15/20231,440,000 shares $60.70 million +9.9%4.1%4.5 $42.15
3/31/20231,310,000 shares $49.13 million -10.3%3.7%4.6 $37.50
3/15/20231,460,000 shares $53.79 million -16.6%4.1%5.7 $36.84
2/28/20231,750,000 shares $55.76 million +1.2%4.7%7.4 $31.86
2/15/20231,730,000 shares $56.33 million +0.6%4.6%8.3 $32.56
1/31/20231,720,000 shares $52.05 million +1.2%4.6%8.1 $30.26
1/15/20231,700,000 shares $49.23 million -1.2%4.6%7.9 $28.96
12/30/20221,720,000 shares $48.19 million -2.3%4.6%7.9 $28.02
12/15/20221,760,000 shares $50.65 million -0.6%4.8%7.9 $28.78
11/30/20221,770,000 shares $52.20 million -3.8%4.8%7.7 $29.49
11/15/20221,840,000 shares $52.20 million -5.2%5.0%7.5 $28.37
10/31/20221,940,000 shares $59.95 million +1.6%5.2%6.9 $30.90
10/15/20221,910,000 shares $54.49 million +1.1%5.1%6.6 $28.53
9/30/20221,890,000 shares $53.11 million -9.1%5.0%6.2 $28.10
9/15/20222,080,000 shares $61.01 million -5.0%5.6%6 $29.33
8/31/20222,190,000 shares $64.82 million +1.4%5.9%5.1 $29.60
8/15/20222,160,000 shares $70.26 million -5.7%5.8%4.2 $32.53
7/31/20222,290,000 shares $85.62 million -3.0%6.1%4.1 $37.39
7/15/20222,360,000 shares $87.41 million +2.6%6.3%4.2 $37.04
6/30/20222,300,000 shares $80.02 million -11.5%6.2%3.8 $34.79
6/15/20222,600,000 shares $81.43 million +11.1%7.0%4.3 $31.32
5/31/20222,340,000 shares $86.91 million -6.8%6.3%4.3 $37.14
5/15/20222,510,000 shares $88.70 million +6.8%6.8%5.1 $35.34
4/30/20222,350,000 shares $83.35 million +15.2%6.4%5 $35.47
4/15/20222,040,000 shares $84.74 million +4.6%5.5%4.4 $41.54
3/31/20221,950,000 shares $70.01 million -3.5%5.4%4.7 $35.90
3/15/20222,020,000 shares $70.17 million +1.5%5.5%5.5 $34.74
2/28/20221,990,000 shares $55.14 million -2.9%5.5%6.3 $27.71
2/15/20222,050,000 shares $54.12 million +5.7%5.6%7.2 $26.40
1/31/20221,940,000 shares $44.79 million -1.5%5.6%7.1 $23.09
1/15/20221,970,000 shares $49.98 million -2.0%5.7%9.2 $25.37
12/31/20212,010,000 shares $46.81 million -2.9%5.8%10 $23.29
12/15/20212,070,000 shares $46.26 million -2.4%6.0%11.3 $22.35
11/30/20212,120,000 shares $41.47 million +7.1%6.1%12.5 $19.56
11/15/20211,980,000 shares $41.88 million -14.3%5.7%11.9 $21.15
10/29/20212,310,000 shares $43.15 million +1.3%6.6%16.3 $18.68
10/15/20212,280,000 shares $43.57 million No Change6.5%15.2 $19.11
9/30/20212,280,000 shares $43.34 million -5.8%6.5%14.1 $19.01
9/15/20212,420,000 shares $43.27 million +0.8%6.9%12.5 $17.88
8/31/20212,400,000 shares $47.09 million +3.0%6.9%11 $19.62
8/13/20212,330,000 shares $45.67 million -2.5%6.7%10.5 $19.60
7/30/20212,390,000 shares $50.07 million -1.2%6.9%10.2 $20.95
7/15/20212,420,000 shares $48.45 million -0.8%7.0%11 $20.02
6/30/20212,440,000 shares $49.19 million -7.9%7.1%11.1 $20.16
6/15/20212,650,000 shares $52.95 million +1.9%7.7%14.4 $19.98
5/28/20212,600,000 shares $49.19 million No Change7.5%15.4 $18.92
5/14/20212,600,000 shares $50.86 million -1.1%7.5%13.4 $19.56
4/30/20212,630,000 shares $46.21 million +3.5%7.6%13.7 $17.57
4/15/20212,540,000 shares $44.20 million +2.8%7.3%13.5 $17.40
3/31/20212,470,000 shares $44.46 million +2.9%7.3%12.6 $18.00
3/15/20212,400,000 shares $46.46 million -6.6%7.1%11.2 $19.36
2/26/20212,570,000 shares $45.98 million +0.8%7.5%12 $17.89
2/12/20212,550,000 shares $48.81 million -1.9%7.5%13.1 $19.14
1/29/20212,600,000 shares $48.28 million +1.6%7.3%12.8 $18.57
1/15/20212,560,000 shares $49.31 million -4.1%7.1%12.6 $19.26
12/31/20202,670,000 shares $53.00 million +3.5%7.5%13.6 $19.85
12/15/20202,580,000 shares $48.63 million -3.4%7.2%13.5 $18.85
11/30/20202,670,000 shares $48.38 million -0.7%7.5%13.8 $18.12
11/15/20202,690,000 shares $52.11 million No Change7.5%14.3 $19.37
10/30/20202,690,000 shares $54.04 million -2.2%7.5%15.1 $20.09
10/15/20202,750,000 shares $57.37 million +2.6%7.7%14.1 $20.86
9/30/20202,680,000 shares $50.25 million +7.2%7.5%12.2 $18.75
9/15/20202,500,000 shares $48.75 million -1.2%7.0%10.6 $19.50

AMPH Short Interest - Frequently Asked Questions

What is Amphastar Pharmaceuticals' current short interest?

Short interest is the volume of Amphastar Pharmaceuticals shares that have been sold short but have not yet been closed out or covered. As of August 15th, investors have sold 4,130,000 shares of AMPH short. 12.07% of Amphastar Pharmaceuticals' shares are currently sold short. Learn More on Amphastar Pharmaceuticals' current short interest.

What is a good short interest ratio for Amphastar Pharmaceuticals?

The short interest ratio, also known as the "days to cover ratio", is calculated by dividing the number of shares of a stock sold short divided by its average trading volume. A short interest ratio ranging between 1 and 4 generally indicates strong positive sentiment about a stock and a lack of short sellers. A short interest ratio of 10 or greater indicates strong pessimism about a stock. AMPH shares currently have a short interest ratio of 8.0. Learn More on Amphastar Pharmaceuticals's short interest ratio.

Which institutional investors are shorting Amphastar Pharmaceuticals?

As of the most recent reporting period, the following institutional investors, funds, and major shareholders have reported short positions of Amphastar Pharmaceuticals: Group One Trading LLC, and Wolverine Asset Management LLC. These positions are disclosed in Form 13F filings with the Securities and Exchange Commission.

What is a good short interest percentage for Amphastar Pharmaceuticals?

Companies that have a short interest as a percentage of float below 10% indicates positive investor sentiment and few short sellers. Stocks with a short interest percentage above 10% is considered high, suggesting some investors are pessimistic about the stock. Companies with a short interest percentage of 20% or more indicates widespread negative sentiment. 12.07% of Amphastar Pharmaceuticals' floating shares are currently sold short.

Is Amphastar Pharmaceuticals' short interest increasing or decreasing?

Amphastar Pharmaceuticals saw a increase in short interest during the month of August. As of August 15th, there was short interest totaling 4,130,000 shares, an increase of 2.7% from the previous total of 4,020,000 shares. Changes in short volume can be used to identify positive and negative investor sentiment. Investors that short sell a stock are betting that its price will decline in the future. An increase in short sale volume suggests bearish (negative) sentiment among investors. A decrease on short sale volume suggests bullish (positive) sentiment.

What is Amphastar Pharmaceuticals' float size?

Amphastar Pharmaceuticals currently has issued a total of 46,490,000 shares. Some of Amphastar Pharmaceuticals' outstanding shares are available for trading, while others are subject to various restrictions. The public float, also referred to as floating shares or "the float", are shares that publicly owned, unrestricted and available to trade on the open market. Amphastar Pharmaceuticals currently has a public float of 34,220,000 shares.

How does Amphastar Pharmaceuticals' short interest compare to its competitors?

12.07% of Amphastar Pharmaceuticals' shares are currently sold short. Here is how the short interest of companies in the industry of "pharmaceutical products" compare to Amphastar Pharmaceuticals: Nuvalent, Inc. (12.40%), Merus N.V. (5.87%), CRISPR Therapeutics AG (25.63%), TG Therapeutics, Inc. (14.84%), Cytokinetics, Incorporated (13.10%), Krystal Biotech, Inc. (12.02%), ACADIA Pharmaceuticals Inc. (5.92%), ADMA Biologics Inc (6.27%), Vaxcyte, Inc. (8.81%), PTC Therapeutics, Inc. (8.18%),

Which stocks are the most shorted right now?

As of the most recent reporting period, the following stocks had the largest short interest positions: Lucid Group, Inc. ($8.00 billion), Spotify Technology ($5.48 billion), AppLovin Corporation ($5.11 billion), Reddit Inc. ($5.02 billion), Coinbase Global, Inc. ($3.99 billion), Charter Communications, Inc. ($3.89 billion), Live Nation Entertainment, Inc. ($3.18 billion), Seagate Technology Holdings PLC ($2.59 billion), ResMed Inc. ($2.55 billion), and Rocket Lab Corporation ($2.52 billion). View all of the most shorted stocks.

What does it mean to sell short Amphastar Pharmaceuticals stock?

Short selling AMPH is an investing strategy that aims to generate trading profit from Amphastar Pharmaceuticals as its price is falling. AMPH shares are trading down $0.20 today. To short a stock, an investor borrows shares, sells them and buys the shares back on the public market later to return it to the lender. Short sellers are betting that a stock will decline in price. If the stock does drop after selling, the short seller buys it back at a lower price and returns it to the lender. The difference between the sell price and the buy price is the trader's profit.

How does a short squeeze work against Amphastar Pharmaceuticals?

A short squeeze for Amphastar Pharmaceuticals occurs when it has a large amount of short interest and its stock appreciates in price. This forces short sellers to cover their short interest positions by buying actual shares of AMPH, which in turn drives the price of the stock up even further.

How often is Amphastar Pharmaceuticals' short interest reported?

Short interest is typically published by a stock exchange once per month. However, NASDAQ publishes a report for U.S. stocks, including AMPH, twice per month. The most recent reporting period available is August, 15 2025.




This page (NASDAQ:AMPH) was last updated on 9/4/2025 by MarketBeat.com Staff
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