Swelling in the ankles and feet (peripheral oedema), along with weight gain, is not a common side effect of CTD-T 12.5/80 Tablet, which contains Telmisartan (an ARB) and Chlorthalidone (a diuretic). These medications usually help prevent fluid retention rather than cause it. Such swelling is more commonly seen with calcium channel blockers. More likely causes include fluid retention due to vasodilation (widening of blood vessels), reduced kidney function, or inadequate blood pressure control. You should consult your doctor to rule out kidney or heart problems and adjust your treatment if needed.