I gave my 26 day old baby 5 drops of vitamin D thinking they were BioGaia colic drops. Is this serious?

Hello ,I would like you to specify the strength used. If it is 400u/gt, you would have given 2000u which is not theoretically a toxic dose. You can skip the next 4 days of vitamin. It would be prudent to monitor his condition (symptoms of diarrhea or constipation, sudden fatigue or change in his wakefulness). If you notice any abnormal signs or symptoms, bring your child in for a medical consultation thank you