Mexico has upped its "estimated" number of COVID-19 deaths to 89,612 and boosted estimates of its total number of cases to 870,699, almost 137,000 more than it previously recognised.
Even with the new toll, Mexico is still in fourth place world wide behind India, which has 95,542 deaths.
But in the case of infections, the number would boost Mexico from eighth place in total cases to fifth behind Russia with about 1.15 million cases.
Mexico has about 76,600 test-confirmed deaths and 733,717 test-confirmed cases.
But officials acknowledge those are significant undercounts because the country does so little testing: only about 1.6 million tests have been done so far.
In a nation of almost 130 million, that means that only about one in 80 Mexicans has ever had a test.
About 40 per cent of all tests are positive because only people with significant symptoms are tested.
Mexico had previously published "estimated" figures based on tests still awaiting results, which sometimes takes weeks.
But the new estimates released on Monday by the Health Department are higher because they were calculated by adding two new groups: those never tested but with symptoms and those who had tests which could not be analysed because the samples were not handled properly.
The new figures also include a proportion of pending results.
Officials revealed on Sunday that almost 96,000 test swabs - equal to about 5 per cent of all tests in Mexico - had to be thrown out because they never reached a lab, arrived too late or were not preserved properly.
The new estimates are likely to revive debate about Mexico's death toll because to date the government has avoided adjusting it upward to account for people who died at home or weren't tested.
Some parts of the country like Mexico City have begun conducting their own recalculations, finding "excess deaths" likely caused by coronavirus were at least double official figures.
The issue is a significant one because President Andres Manuel Lopez Obrador has frequently compared Mexico's death rates to those of other countries to convince the public his administration isn't doing a bad job.
Mexico's top coronavirus official said Sunday definitive data on the country's death toll from COVID-19 won't be available for "a couple of years".