Amphastar Pharmaceuticals (AMPH) Short Interest Ratio & Short Volume $26.44 +0.39 (+1.50%) As of 04:00 PM Eastern Add Compare Share Share Short Interest Stock AnalysisAnalyst ForecastsChartCompetitorsEarningsFinancialsHeadlinesInsider TradesOptions ChainOwnershipSEC FilingsShort InterestSustainabilityTrendsBuy This Stock Amphastar Pharmaceuticals Short Interest DataAmphastar Pharmaceuticals (AMPH) has a short interest of 4.10 million shares, representing 11.79% of the float (the number of shares available for trading by the public). This marks a 2.24% increase in short interest from the previous month. The short interest ratio (days to cover) is 7.0, indicating that it would take 7.0 days of the average trading volume of 488,662 shares to cover all short positions.Current Short Interest4,100,000 sharesPrevious Short Interest4,010,000 sharesChange Vs. Previous Month+2.24%Dollar Volume Sold Short$106.11 millionShort Interest Ratio7.0 Days to CoverLast Record DateMay 31, 2025Outstanding Shares47,139,000 sharesFloat Size34,780,000 sharesShort Percent of Float11.79%Today's Trading Volume506,968 sharesAverage Trading Volume488,662 sharesToday's Volume Vs. Average104% Short Selling Amphastar Pharmaceuticals? Sign up to receive the latest short interest report for Amphastar Pharmaceuticals and its competitors with MarketBeat's FREE newsletter. Email Address Skip Charts & View Short Interest HistoryShort Interest ChartDays to Cover ChartShort Percent of Float ChartAMPH Short Interest Over TimeAMPH Days to Cover Over TimeAMPH Percentage of Float Shorted Over Time Amphastar Pharmaceuticals Short Interest History Export to ExcelReport DateTotal Shares Sold ShortDollar Volume Sold ShortChange from Previous ReportPercentage of Float ShortedDays to CoverPrice on Report Date 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 Get the Latest News and Ratings for AMPH and Related StocksEnter your email address below to receive the latest news and analysts' ratings for Amphastar Pharmaceuticals and its competitors with MarketBeat's FREE daily newsletter. 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 $45.76Elon’s BIGGEST warning yet? 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Click here to see why Tesla's about to prove everyone wrong... again. 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 $17.88Trump’s true trade war strategy (Ad)The media and financial pundits are all misreading Trump’s actions. They think Trump wants to make Canada the 51st state because he’s desperate for critical minerals… They think his involvement in Ukraine is just another resource grab… They think his tariffs will wreck the economy… But they’re all missing the bigger picture.This is fast becoming the world’s most sought-after resource. 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 8/31/20202,530,000 shares $51.56 million +0.8%7.1%9.9 $20.38 8/14/20202,510,000 shares $51.05 million -6.3%7.1%8.6 $20.34 7/31/20202,680,000 shares $53.65 million +1.9%7.8%7.8 $20.02 7/15/20202,630,000 shares $53.31 million -6.7%7.6%7.6 $20.27 6/30/20202,820,000 shares $62.38 million -8.1%8.2%8.2 $22.12 6/15/20203,070,000 shares $61.22 million -4.1%8.9%9.1 $19.94 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 May 31st, traders have sold 4,100,000 shares of AMPH short. 11.79% 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 7.0. 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: Simplex Trading 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. 11.79% 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 in the month of May. As of May 31st, there was short interest totaling 4,100,000 shares, an increase of 2.2% from the previous total of 4,010,000 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 47,139,000 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 34,780,000 shares. How does Amphastar Pharmaceuticals' short interest compare to its competitors? 11.79% 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: Vaxcyte, Inc. (10.93%), Merus (7.12%), Rhythm Pharmaceuticals, Inc. (8.24%), Akero Therapeutics, Inc. (10.75%), Avidity Biosciences, Inc. (14.07%), PTC Therapeutics, Inc. (6.52%), Cytokinetics, Incorporated (12.42%), Sarepta Therapeutics, Inc. (10.50%), Krystal Biotech, Inc. (11.82%), ACADIA Pharmaceuticals Inc. (13.96%), Which stocks are the most shorted right now? As of the most recent reporting period, the following stocks had the largest short interest positions: SPDR S&P 500 ETF Trust ($64.96 billion), Invesco QQQ ($27.88 billion), iShares Russell 2000 ETF ($19.94 billion), iShares 20+ Year Treasury Bond ETF ($9.69 billion), Strategy Incorporated ($8.58 billion), SPDR S&P Biotech ETF ($5.72 billion), Invesco S&P 500 Equal Weight ETF ($5.45 billion), iShares iBoxx $ Investment Grade Corporate Bond ETF ($4.70 billion), Charter Communications, Inc. ($4.54 billion), and Industrial Select Sector SPDR Fund ($4.49 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 up $0.30 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 increases 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 May, 31 2025. More Short Interest Resources from MarketBeat Related Companies Vaxcyte Short Squeeze Merus Short Squeeze Rhythm Pharmaceuticals Short Squeeze Akero Therapeutics Short Squeeze Avidity Biosciences Short Squeeze PTC Therapeutics Short Squeeze Cytokinetics Short Squeeze Sarepta Therapeutics Short Squeeze Krystal Biotech Short Squeeze ACADIA Pharmaceuticals Short Squeeze Short Interest Tools Stocks to Short Largest Short Interest Positions Short Interest Increases Short Interest Decreases Short Interest Reporting Dates This page (NASDAQ:AMPH) was last updated on 6/12/2025 by MarketBeat.com Staff From Our PartnersTrump’s Exec Order #14154 could be a “Millionaire-Maker”Former Presidential Advisor, Jim Rickards, says Trump could “rewire our economy and hand millions of Americans...Paradigm Press | SponsoredElon’s NEXT Big IPO?Cancel your internet TODAY!? 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