In India, the semi medicinal use of tea brew is noted in 1662 by Mendelslo:

           At our ordinary meetings every day we took only thay, which is commonly used all over the Indies, not only among those of the country, but also among the Dutch and the English, who take it as a drug that cleanses the stomach, and digests the superfluous humours, by a temperate heat particular thereto.

— Indian Food A Historical Companion by Achaya K. T.

In 1689 Ovington records that tea was taken by the banias in Surat without sugar, or mixed with a small quantity of conserved lemons, and that tea with some spices added was used against headache, gravel and gripe. The tea leaves for such use may have come from China.

While experimenting to introduce tea in India, British colonists noticed that tea plants with thicker leaves also grew in Assam, and these, when planted in India, responded very well. The same plants had long been cultivated by the Singphos tribe of Assam, and chests of tea supplied by the tribal ruler Ningroola. The Assamese and Chinese varieties have been regarded in the past as different related species, but are now usually classified by botanists as the same species, Camellia sinensis. 

In the early 1820s, the British East India Company began large-scale production of tea in Assam, India, of a tea variety traditionally brewed by the Singpho people.[2] In 1826, the British East India Company took over the region from the Ahom kings through the Yandaboo Treaty. In 1837, the first English tea garden was established at Chabua in Upper Assam; in 1840, the Assam Tea Company began the commercial production of tea in the region. Beginning in the 1850s, the tea industry rapidly expanded, consuming vast tracts of land for tea plantations. By the turn of the century, Assam became the leading tea-producing region in the world