Background: Estimated glomerular filtration rate (eGFR) is accepted as the best indicator of kidney function and commonly assessed from serum creatinine (Cr) and cystatin C (Cys-C) based equations. The present cross-sectional, observational study aimed to assess eGFR using a new and validated Full Age Spectrum (FAS) equation and compared with eGFR assessed using old and established equations in hypertensive patients. Materials and Methods: Overall, 60 subjects were recruited for the study, including 30 hypertensive patients and 30 age and sex matched healthy subjects. Serum creatinine and cystatin C were measured using commercial biochemical kits. These levels were used to derive and compare eGFR using our different equations, namely, Cockcroft and Gault (CG), Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease-epidemiology collaboration (CKD-EPI), and FAS equation. Student t-test was used for comparison between two groups and One-way ANOVA test was used to find multiple comparison with-in the hypertensive and control group. Pearson’s Univariate correlation followed by multiple linear regression analysis was applied to find independent predictors of eGFR. All data were analyzed using Sigma-Stat. Results: There was significant difference found in the eGFR levels using different equations in hypertensive subjects as compared to healthy subjects (P<0.01). With–in hypertensive subjects and with-in heathy subjects, a significant difference was also reported (both P<0.01). For FAS-based GFR, age was found as independent predictor of eGFR by all FAS equations. eGFR estimated using Cr based equations resulted in significant difference in categorizing number of subjects into CKD v/s non-CKD depending on their eGFR levels. But there was no difference found for the above in serum cystatin C based equations (P=0.26). Conclusion: Present data showed that eGFR derived using all set of equations resulted in variable eGFR levels. But, use of Cr based equations instead of Cys-C or combine Cr-Cys based equations resulted in wide variation i.e. change in GFR due to change in marker.