When to take a probiotic in the morning or evening - manufacturer's recommendations
By far the easiest way is when the manufacturer of a probiotic provides an exact prescription for taking it. However, this is not a very common practice.
When to take a probiotic in the morning or evening - general recommendations
When the product label does not contain this information, or the source of probiotics will be natural products such as pickles, yogurts, etc., then it will be more beneficial to consume probiotics on an empty stomach or 30 minutes before a meal, according to a report by researchers from Canada (Tompkins TA, et al., 2011). The conclusions of this study involve bacteria of the Bifidobacterium and Lactobacillus species.
In the case of Saccharomyces boulardii mushrooms, the timing of administration will not make much difference.
Most people will therefore find it easier to consume probiotics on an empty stomach, such as in the morning.
When to take a probiotic in the morning or evening - more benefits
However, the results of a new scientific study (Wastyk HC, et al., 2021) suggest that even more health benefits can be obtained by consuming several servings of probiotics throughout the day.
So maybe, instead of asking the question: probiotic in the morning or in the evening, it's better to think about how to consume probiotics both in the morning and in the evening, and maybe a few more times during the day.