** Shares of Australia's NIB Holdings NHF.AX fall as much as 7% to A$5.58
** Stock hits lowest level since April 23, 2021
** NIB estimates it will report operating loss for first half and lowers outlook as a boost in claims for its New Zealand operations weighs on returns
** The insurer is set for its weakest trading session since late August
** Stock has fallen 18.81% this year, as of last close
(Reporting by Nichiket Sunil in Bengaluru)
((nichiket.sunil@thomsonreuters.com))