INSP Shorts Build Ahead of a Guidance-Tested Print

Inspire Medical Systems heads into its November 3 earnings report with short sellers sitting at their most aggressive position in months, even as the borrow market remains wide open.

Short interest has climbed to nearly 15% of the free float, up roughly 10% over the past month and 4.5% over the past week, making it one of the more heavily shorted names in the medtech space. That build has happened despite very loose borrow conditions: availability stands at 901%, meaning there are roughly nine shares available to lend for every one already borrowed. Borrowing costs, while up sharply in percentage terms over the past week, remain low in absolute terms at 0.40%. The short interest story here is about conviction, not squeeze dynamics. Options positioning adds to the cautious tone, with the put/call ratio at 0.99, above its 20-day average of 0.82, though the move is not extreme by the stock's own standards. The shares themselves have dropped 5.4% over the past week and 3.9% over the past month, now trading at $67.21.

The debate around INSP centres on a single fault line: whether the reimbursement headwinds that forced a guidance cut earlier this year are a temporary disruption or a structural problem. The bear case is direct. The company lowered its 2026 revenue guidance from $1,003 to 1,013 million to $950 to 1,000 million, citing coding and reimbursement uncertainty that is dampening domestic procedure volumes and potentially discouraging ENT specialists from performing the therapy. Barclays initiated coverage last month with an Underweight rating and a $65 target, below the current price, the clearest statement of scepticism from a major firm. Truist Securities, also on Hold, raised its target from $62 to $78, a wide range that reflects how much uncertainty the Street is trying to price. Bulls counter that the global hypoglossal nerve stimulation market retains double-digit growth potential, the company has been investing heavily in advertising ($114.9 million in 2025, up 21%), and that profitability improvements are still projected for 2026. Freedom Capital and Stifel both carry Buy ratings with targets in the $80 to $97 range. The consensus price target of $68 sits nearly dead level with the stock, an unusually tight spread that reflects genuine disagreement rather than directional conviction.

One institutional angle worth noting: BlackRock lifted its stake to 14.4% of the class in its most recent filing, up from 11.3% previously, making it the dominant holder by a wide margin. Soleus Capital and AQR both appear to have built new positions exceeding 6% of shares during the summer. These are sizable additions into a stock that has been falling. At the same time, some earlier backers have been moving the other way. FMR cut from 8.3% to 2.5%, and Marc Stad exited entirely from an 8% position. The insider activity over the past 90 days is limited to small director grants and a single modest open-market sale, none of it directionally significant going into the print.

The August quarter report produced a 15% one-day rally and a 13% five-day gain, so the stock can move sharply on results. This print is less about whether the growth story remains intact over the long run and more about whether management can offer any clarity on the reimbursement environment that has made the near-term trajectory so difficult to model.