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The five most heavily shorted stocks traded on the Nasdaq all saw increases in short interest between the April 30 and May 15 settlement dates. That was most apparent in AMD and MannKind, with the latter shooting up to the number three spot on the list.

Note that the five most shorted Nasdaq stocks all had more than 110,000 shares short at the end of the month.

The number of Sirius XM Holdings Inc. (NASDAQ: SIRI) shares short increased by more than 6 million to about 155.73 million early in the month. That was 6.8% of the total float, as well as the highest level of short interest so far this year. At the current average daily volume, it would still take about nine days to cover all short positions. Sirius was one of our cheap stocks with big upside during the period. Short sellers watched the share price pull back about 3% during the two weeks between settlement dates, and a bit more since. Shares closed Wednesday at $3.89, in a 52-week trading range of $3.14 to $4.04.

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Advanced Micro Devices Inc. (NASDAQ: AMD) had more than 119.55 million shares short by the middle of the month, up 10.2% from the previous settlement date. The most recent reading totaled 18.9% of the company’s float, and the days to cover jumped to more than 10 from less than five in the previous period. AMD had trouble finding some love after its analyst day. The share price ended the two weeks about 1% higher than where it began, though it has fallen more than 5% since. The stock closed at $2.28 on Wednesday, and the 52-week range is $2.14 to $4.80.

MannKind Corp.’s (NASDAQ: MNKD) short interest, at almost 112.95 million shares as of May 15, was up 11.9% from the previous period. Note that it was 44.2% of the total float, as well as the highest short interest in at least a year. The days to cover dropped from more than 20 to less than 15. Shares ended Wednesday at $5.27, in a 52-week range of $3.46 to $11.48. The stock saw a share price decline of 21.0% in the two-week short-interest period, during which Mannkind reported a quarterly net loss. The stock has recovered since.

The short interest in Frontier Communications Corp. (NASDAQ: FTR) rose fractionally from the previous period to around 111.87 million shares, or 11.3% of the telecom’s float. The number of shares short had been on the decline since last December. The days to cover dropped from more than 17 to less than seven as the daily volume traded has increased. During the short interest period, shares fell to a new 52-week low, retreating about 21% in that time. They are down more than 20% year to date. Shares closed Wednesday at $5.84 and have a 52-week trading range of $5.44 to $8.46.

A 1.8% bump in short interest brought Intel Corp. (NASDAQ: INTC) to around 110.42 million shares short in mid-May. That totaled 2.3% of the company’s float and was still the second lowest number of shares short in at least a year. The days to cover remained more than four. In the period, the stock was a Jefferies franchise pick. Shares rose fractionally in the short interest period, as did the Nasdaq. The stock is now down around 7% year to date and closed most recently at $33.71. Shares have traded between $26.66 and $37.90 in the past year.

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Rounding out the top 10 were BlackBerry Ltd. (NASDAQ: BBRY), Microsoft Corp. (NASDAQ: MSFT), Apple Inc. (NASDAQ: AAPL), Express Scripts Holding Co. (NASDAQ: ESRX) and Micron Technology Inc. (NASDAQ: MU). Short sellers retreated from Microsoft and Micron during the period. However, they moved on Apple, with its shares near an all-time high and iPhone sales bound to slow at some point, boosting the number of shares short by more than 25%.