Malnutrition poses a significant global health challenge, affecting various age groups, with infants under 6 months being particularly vulnerable. Vitamin B12, an essential micronutrient critical for neurological development, has been identified as a key player in the overall health of both mothers and infants.

To find the correlation between serum vitamin B12 levels in infants, 1–6 months of age with severe malnutrition and maternal levels at tertiary care hospitals in western Rajasthan.

The cross-sectional study was conducted in the UNICEF Regional Center of Excellence-supported Nutrition Rehabilitation Center in Rajasthan, India, through simple random sampling. One hundred ten infants with their mothers were enrolled after consent and approval from the Institutional Ethics Committee.

Severe malnutrition predominantly affected infants aged 1–2 months, with 77% born small for gestational age and 66.4% belonging to the multiple birth order group. Serum vitamin B12 levels showed a significant positive correlation between mothers and infants (p < 0.001), while exclusive breastfeeding correlated positively with age-appropriate milestones (p = 0.033).

The findings emphasize the importance of targeted interventions addressing maternal and infant nutrition, with a focus on ensuring adequate vitamin B12 levels.