UPDATE1-Private equity considers bidding for NBTY - source

* NBTY has market value of about $2.3 billion

* Carlyle, Blackstone interested in firm - source

(Adds details about private equity deals, byline)

By Megan Davies

NEW YORK, July 14 (Reuters) - Private equity firms Blackstone Group LP (BX.N) and Carlyle may acquire U.S. nutritional supplements maker NBTY Inc NTY.N, a source familiar with the situation said on Wednesday.

The private equity firms are working separately from each other, not as a consortium, the source said. It was unclear how advanced the plans were.

News of a potential deal was earlier reported by the Wall Street Journal which said Blackstone and Carlyle are in talks to buy the firm.

The companies could not be immediately reached for comment by Reuters outside regular U.S. business hours.

NBTY, which has a market value of about $2.3 billion, posted a quarterly profit in April and missed market expectations by a wide margin, hurt by increased spending on television advertising.

Private equity deals, put on hold when the credit crisis shut off access to cheap debt, have been making a revival.

Earlier in July, BC Partners [BCPRT.UL] and Silver Lake Partners [SILAK.UL] announced a deal to buy U.S. healthcare services firm MultiPlan from two other buyout shops. That deal was worth about $3.1 billion, sources said at the time.

(Reporting by Megan Davies in New York and Sakthi Prasad in Bangalore; Editing by Valerie Lee)