Ishant had returned with a career-best figures of seven for 74 to guide India to a 95-run win over England in the second Test at Lord's, but he missed the second Test after picking up an injury in his left ankle.
He was replaced in the third Test here by Rajasthan pacer Pankaj Singh.
"Ishant will definitely not be fit for the fourth Test. We will have to discuss the matter but as of now he won't be available for the next Test," Dhoni said when asked if the Delhi pacer will be fit for the fourth Test.
With Ishant unavailable for the fourth Test, Dhoni will certainly have a lot of thinking to do in terms of getting his first XI right.