BackgroundDespite unprecedented socio-economic growth experienced by Indians in the past few decades, and a long history of anti-anaemia public health measures, prevalence of anaemia in Indian non-pregnant women of reproductive age group (NPWRA) has not declined. This warrants a firm understanding of what explains the anaemia situation over time, preferably by sub-populations. Therefore, we aimed to examine the trends of anaemia in tribal NPWRA (least privileged) and compare with the trends in the NPWRA of general caste (most privileged) between 1998 to 2021. Additionally, the study also explored explanation of any decline and tribal/general narrowing of these trends.MethodsWe studied four rounds of National Family Health Survey (1998–99, 2005–06, 2015–16, 2019–21). We examined the trend of anaemia (haemoglobin < 12 g/dl) and its possible determinants in tribal and general NPWRA and estimated the portion of “decline” and “narrowing” that could be explained by theunderlyingandintermediatedeterminants (wealth, education, residence, parity and food security) using multiple logistic regression.ResultsThe distribution of determinants improved over 23 years in both the groups but more in tribals. But anaemia either remained unchanged or increased in both except 7.1 points decline in tribals between 2006–2016, leading also to 7 points narrowing of tribal/general gap. The modest attenuation of beta coefficients representing the change of anaemia prevalence (log of odds) in tribals from -0.314(-0.377, -0.251) to -0.242(-0.308, -0.176) after adjustment with determinants could explain only 23% of the decline. Similarly, only 7% of the narrowing of the tribal/general anaemia gap could be explained.ConclusionsThe structural determinants wealth, education, food security, parity and urban amenities improved immensely in India but anaemia did not decline in this 23-year period. This implies that the “usual suspects” – the structural determinants are not the main drivers of anaemia in the country. The main driver may be absolute and/or functional deficiency status of micronutrients including iron attributable to inadequate uptake and absorption of these elements from Indian diets; and therefore, their effects are noticeable in every socio-economic stratum of India. Future research for aetiologies and new interventions for anaemia alleviation in India may focus on these factors.