* FTSE 100 down 0.2%, FTSE 250 up 0.2%
* NMC tops main index
* Nichols slumps after profit alert (Adds news items, analyst comments, updates share prices)
Dec 23 (Reuters) - A drop in healthcare and financial stocks led London's main index away from a near five-month high on Monday and halted its eight-day rally, though NMC Health outperformed after launching a review of its books following an attack by a short-seller.
The FTSE 100 edged 0.2% lower in holiday-thinned trade, as investors locked in profits from earlier this month. The FTSE 250 added 0.2%, up for the third straight session.
"It's been a strong run up to Christmas for the stock markets and it seems traders are taking a little breather in this shortened trading week," OANDA analyst Craig Erlam said.
"Stocks are trading slightly in negative territory at the start of the week, although there's very little we can read into this, given the lower festive volumes and news flow."
NMC, whose shares have nearly halved in value since Muddy Waters criticised the healthcare group's financials last week, jumped 23% and was set for its best day since floating in 2012.
However, that was not enough to support the blue-chip bourse, which fell after its best run since May 2017.
A breakthrough in U.S.-China trade talks and Prime Minister Boris Johnson's election victory had helped the index surge nearly 5% in the last two weeks, though some of that momentum eased after Johnson's hard line on a trade agreement with the European Union revived fears of a chaotic Brexit.
Still, the exporter-heavy FTSE is on course for its best month since June and the more domestically-focussed midcaps are on track for a fourth straight month of gains. Both benchmark indexes look set for their ninth month of gains this year.
GlaxoSmithKline gave up nearly 1%, in line with losses in the broader market. Separately, the U.S. Food and Drug Administration on Saturday declined to approve its drugs division's long-acting HIV injection.
AIM-listed Nichols dropped 17% to its lowest level since Jan. 3, after the Vimto soft drinks maker warned on its 2020 profit.
Mid-cap Finablr, which fell in the previous four sessions, advanced 7%. The payments firm is co-chaired by the founder of NMC Health. (Reporting by Shashwat Awasthi in Bengaluru, editing by Larry King and Saumyadeb Chakrabarty)