Can the drops be added to formula milk?

Yes the drops can be mixed with breast milk and/or formula. The only thing to consider when adding the drops to liquids is the temperature. Do not add to liquids warmer than 37°C/99°F. If adding to liquids make sure to consume within the same day.

Do I need to take Lactobacillus reuteri every day?

Yes, since the intestinal levels are depleted within about a week after discontinuing use. The resident microbiota of an individual is relatively fixed and thereby highly resistant to the establishment of “newcomers”. Even an indigenous bacterium like Lactobacillus reuteri should be taken on a regular basis, since most people of modern society does not get colonized by Lactobacillus reuteri during infancy. By taking BioGaia probiotics regularly you maintain the total daily supply of lactobacilli.