DaVita, a company that provides dialysis services, saw shares tumbling Friday after issuing a weak outlook amid rising care costs, while big investor Berkshire Hathaway offloaded some shares in a preplanned agreement.

The health-care stock fell more than 12% Friday. The Colorado-based company said it expects its 2025 adjusted profit per share to be between $10.20 and $11.30, compared to analysts’ average expectation of $11.24 per share, according to LSEG.

The disappointing guidance underlined increasing patient care costs due to center closure costs and health benefit expenses. In the fourth quarter, the company incurred charges for closures of its dialysis centers in the U.S. totaling $24.2 million.

Still, DaVita’s fourth-quarter earnings of $2.24 per share on an adjusted basis topped analysts’ estimates of $2.13 per share per LSEG.

Separately, DaVita’s largest institutional investor Berkshire Hathaway sold 203,091 shares on Tuesday to reduce its stake to 45%, worth nearly $6.4 billion, a regulatory filing Thursday night showed.

The sale was part of a share repurchase agreement the two parties reached back in April. DaVita agreed  to buy back shares to reduce Berkshire’s ownership stake to 45% on a quarterly basis.

Warren Buffett’s conglomerate first invested in DaVita in 2011. As of the end of September, DaVita was Berkshire’s 10th largest equity holding.

Check out the companies making big moves midday.

Novo Nordisk — The Danish drugmaker stock added 6.27% after saying late Tuesday it was halting Ozempic’s kidney disease treatment trial after a committee said an analysis showed signs of success. Eli Lilly, which makes diabetes drug Mounjaro, rose 4.48%.

DaVita, Fresenius Medical Care, Baxter International — Shares of dialysis services providers DaVita and Fresenius Medical Care sank 16.86% and 17.57%, respectively, on Novo Nordisk’s news. Baxter International, which makes products for chronic dialysis therapies, slid 12.27%.

Exxon Mobil, Pioneer Natural Resources — Exxon Mobil shares fell 3.59% after the largest U.S. oil and gas producer agreed to buy shale rival Pioneer Natural Resources for $59.5 billion in an all-stock deal, or $253 per share. Pioneer stockholders will receive 2.3234 shares of Exxon for every Pioneer share held. The deal, Exxon’s biggest since its acquisition of Mobil, is expected to close in the first half of 2024. Shares of Pioneer rose 1.44% following the news.

Humana — Shares slipped 1.39% after CEO Bruce Broussard said he will step down from his position in the latter half of 2024. The company named Jim Rechtin of Envision Healthcare as his successor.

Amgen — The biopharma stock added 4.55% following an upgrade from Leerink to outperform. Analyst David Risinger cited an expanding earnings multiple and pipeline newsflow as catalysts.

Shoals Technologies — Shares gained 5.26% after being upgraded to buy from neutral at Goldman Sachs. The investment bank cited valuation and the potential for gross margin upside.

Ally Financial — The provider of loans to midsize businesses dropped 2.12% after CEO Jeffrey Brown announced plans to step down, effective Jan. 31, 2024.

Walgreens Boots Alliance — The pharmacy chain added 0.98% after former Cigna executive Tim Wentworth was named CEO effective Oct. 23.

Coherent — The stock popped 5.23% in midday trading. Coherent announced Tuesday that Japanese companies will invest $1 billion in Coherent’s silicon carbide business. On Wednesday, B. Riley upgraded shares to buy from neutral, saying Coherent’s silicon carbide business could be worth more than the Street’s current estimate.

Plug Power — The battery company climbed 5.31% after forecasting a sharp rise in revenue to roughly $6 billion by 2027, according to a regulatory filing.

Take-Two Interactive Software — Shares gained in midday trading but closed 0.34% lower after being upgraded by Raymond James to outperform from market perform. The firm said it sees a path to more consistent video game releases and a reasonable valuation based on Take-Two Interactive’s Grand Theft Auto 6 release soon.

— CNBC’s Michael Bloom, Hakyung Kim, Yun Li and Lisa Han contributed reporting.