Ay, observing baby's poop and skin is usually the telltale sign, kung smooth at yellowish ang tae niya and walang rashes or eczema, most likely okay na ang formula sa kanya, pero kung laging constipated, may loose stools, or sobrang gasa at colicky, it might not be the right fit. A few of us moms tried switching formulas kasi ang babies namin were really uncomfortable, and nakita namin talaga ang difference sa behavior and digestion within a few days, so if you're concerned, best to run it by your pedia first para ma-guide kayo on what to switch to!