(Adds context and 2024 outlook in paragraph 1, details on debt, revenue, EBITDA and background from paragraph 3)

BARCELONA, May 14 (Reuters) - Spanish drugmaker Grifols , battling a plunge in its share price this year, swung to a first-quarter net profit of 21 million euros ($23 million) from a year-ago loss and said on Tuesday it was on track to meet its 2024 outlook.

Grifols said it plans to continue reducing its debt this year thanks to divestments, an increase in its adjusted earnings before interest, taxes, depreciation and amortisation (EBITDA), and some "liquidity improvements". It did not elaborate.

Its leverage ratio fell to 7.9 times EBITDA from 8.4 times at the end of 2023, Grifols said.

Revenue reached 1.6 billion euros in the first quarter, while its adjusted EBITDA rose to 350 million euros, accounting for 21.6% of net revenue, up from 19.3% a year ago.

Its 2024 guidance forecasts full-year revenue over 7 billion euros and an adjusted EBITDA above 1.8 billion euros.

Since early January, short-sheller fund Gotham City Research has released several reports accusing Grifols of overstating earnings and understating debt. Grifols' market value has shed several billion euros since then.

The company has denied any wrongdoing although it has announced governance changes and had to revise its reported leverage higher after market supervisor CNMV required that it change its calculations.

Grifols said last month its debt-to-EBITDA ratio according to profit-and-loss accounting was 8.4 times in 2022 and in 2023, compared to the ratios of 7.1 and 6.3 times, respectively, it had earlier reported.

An investigation by the CNMV found no significant errors in the amounts Grifols reported but identified "deficiencies in the detail and accuracy of breakdowns" in some years.

When Gotham City questioned Grifols' reported third-quarter leverage ratio of 6.7 times in the third quarter of 2023, it said the ratio was close to 10 to 13 times EBITDA.

($1 = 0.9246 euros) (Reporting by Joan Faus, Editing by Andrei Khalip and Emelia Sithole-Matarise)