Lonmin said refined platinum output for the year to end-September rose 74 percent to 759,695 ounces from the previous financial year.
The miner said the annual output was the highest level since 2007.
Lonmin posted platinum sales of 751,560 ounces for the year, also the highest in eight years and beating a guidance of 730,000 ounces.
Lonmin, under pressure from labour unrest, rising costs and weak platinum prices, said last month it plans to raise $400 million in a rights issue of new shares and will proceed with a plan to cut 6,000 jobs in the face of depressed prices.
The moves, along with a debt restructuring, are last-ditch efforts to turn round a company that has seen its share price fall to record lows this year.
The miner, which releases its annual financial results on Nov. 9, said on Monday the results were expected to show an operating loss of $207 million, before impairment charges of $1.85-$2.05 billion.
“The impairment charge is primarily driven by lower PGM prices and the business plan which has an impact on future discounted cash flows over the life of mine business plan across the group’s operations,” Lonmin said in a statement.
London-listed Lonmin shares, down 86 percent so far this year, were trading nearly 3 percent lower at 24.75 pence as of 0918 GMT.