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Fast Radio Bursts (FRBs) are short lived ($\sim$ msec), energetic transients(having a peak flux density of $\sim$ Jy) with no known prompt emission inother energy bands. We present results of a search for prompt X-ray emissionsfrom 41 FRBs using the Cadmium Zinc Telluride Imager (CZTI) on AstroSat whichcontinuously monitors $\sim70\%$ of the sky. Our searches on various timescalesin the 20-200 keV range, did not yield any counterparts in this hard X-rayband. We calculate upper limits on hard X-ray flux, in the same energy rangeand convert them to upper bounds for $\eta$: the ratio X-ray to radio fluenceof FRBs. We find $\eta \leq 10^{8-10}$ for hard X-ray emission. Our resultswill help constrain the theoretical models of FRBs as the models become morequantitative and nearer, brighter FRBs are discovered.

Prompt X-ray emission from Fast Radio Bursts -- Upper limits with AstroSat