Did you recently change the oil and the filter?
If so, you need to fill up the sight glass to full, idle it for awhile (I would advise less than 60 seconds), check the oil level again and fill the sight glass back up to the high mark.
A significant amount of oil gets sucked into the oil filter and causes the oil level in your sight glass to drop. You need to add more oil to compensate for this.
1999 Trx440ex: SOLD
2005 Trx450R: HRC, FMF, G-Force, Cobra, Burgard
Food for thought:
*Jet kits are not upgrades
* DG accessories are nothing to brag about
*Top speed is worthless