The company produced 22,100 ounces of gold in the September quarter, impacted by reduced working faces, heavy rainfall and a work stoppage at Aurora in Guyana, its only mine.
It reported all-in sustaining costs of US$1,882/oz and production so far this year of 96,000oz.
It had expected to produce 145,000-160,000oz in 2019.
The company had twice downgraded its production guidance in 2018, one of the triggers for a bitter battle to overhaul the board, led by founder and former chairman Patrick Sheridan who claimed the company had lost C$1 billion in value since 2016.
They reached a settlement earlier this year, with the miner to seek a new CEO, after it had cut 43% of reserves and decided to further optimise a mine optimisation plan done by Roscoe Postle Associates.
Interim CEO Allen Palmiere said the company had started "a comprehensive mine, production and cost savings review plan to make the necessary changes and improvements to increase productivity and profitability".
He said RPA had been appointed to assist in the latest review and he did not expect it to materially change the total reserves to be mined over the previously published RPA report.
"Management does not consider it appropriate to provide updated guidance ranges or any forward projections until the review is completed," he said.
The review is slated for delivery in the first quarter of 2020.
Palmiere said full year costs were likely to be in line with year-to-date costs but some cost improvements were expected to be realised "almost immediately".
Guyana Goldfields said it ended the quarter with $24.8 million in cash and cash equivalents.
Along with cash flow, it said the money should sufficiently fund the necessary planning work, accelerated stripping and underground development for the rest of 2019 and 2020, "subject to the impact of the ongoing review of the life of mine plan".
Its shares, which were trading about C$1.80 a year ago, hit a 52-week low intraday of 73c - their lowest point since 2008.
They closed at 74c, to capitalise it at $129.2 million (US$98.15 million).
