The folic acid (iron) tablets were given to them as part of Haryana Health Department's supplementation programme to combat anaemia, they said.
There was no major cause for worry as the students had minor side effects after consuming the tablets, the officials said.
Around 150 students, all of them girls, fell sick in Jind, 96 in Hisar and 50 in Sonipat, they said.
Most of them were discharged after treatment, the officials said.
Fifteen lakh children were administered the tablets in schools in 20 districts yesterday, the officials said.
Seventy of them suffered from mild side effects and were provided proper treatment yesterday itself, they said.