Yes, appropriately certified RO systems can reduce nitrate/nitrite. Verify an exact NSF/ANSI 58 nitrate/nitrite claim and test well water because nitrate concentration can change over time.
Why carbon is not enough
Activated carbon is useful for chlorine and many organic compounds, but nitrate is dissolved and typically requires a different treatment mechanism.
NSF/ANSI 58 includes nitrate/nitrite reduction
Nitrate/nitrite is an optional performance claim under NSF/ANSI 58. Many certified RO products carry it, but not every Standard 58 product automatically does.
Private wells need ongoing testing
Nitrate can enter groundwater from fertilizers, septic systems and other land-use sources. CDC includes nitrate among chemicals that can contaminate tap water.
A treatment system should not replace periodic water testing.
Point-of-use vs whole-house treatment
RO is commonly used at the drinking-water tap. Whole-house nitrate treatment can require different system sizing and operating economics.
How to verify treatment claims for Does Reverse Osmosis Remove Nitrates?
Start with the contaminant or water-quality problem, then verify the exact finished system. Technology labels such as reverse osmosis, activated carbon, ion exchange or ultrafiltration describe a treatment mechanism; they do not prove that every product using that mechanism has the same reduction claims. For health-related contaminants, look for model-specific certification or a performance data sheet tied to the exact unit.
NSF/ANSI 42 commonly covers aesthetic effects such as chlorine taste and odor, NSF/ANSI 53 covers specified health-effect reductions, and NSF/ANSI 58 applies to reverse-osmosis systems. The presence of a standard number does not mean every optional contaminant claim in that standard was certified, so the individual listing still matters.
Flow, installation and three-year ownership cost
A filter that treats the right contaminant can still be a poor fit if the household dislikes its flow rate, reservoir workflow or installation requirements. Compare faucet flow, daily production, drain requirements, available cabinet or counter space and whether a powered pump or dedicated faucet is needed. Renters should give extra weight to reversible installations.
Then annualize the consumables. Add prefilters, membranes, postfilters or proprietary cartridges over at least three years and consider availability where you live. Higher-priced hardware can be the better value when filters last longer and remain easy to source; inexpensive hardware can become costly when several proprietary cartridges need frequent replacement.