If you look at the topic of fatigue in a broader way than just drinking B vitamins, then use 60 mg of coenzyme Q10 for 60 days. If the same in the autumn-winter-spring period, then this is another 1 g of omega-3 acids from fish oil. This approach will provide real cellular energy.
It is also useful to think about the causes of fatigue, since they can be as in the disturbed microflora, the presence of intoxication with constipation, low thyroxine levels, impaired microcirculation against the background of insufficient water intake ... See , these are only those moments that are not striking, and which a person does not usually take into account.
Try this online test, it might suggest the reasons for increased fatigue https://www.pobedi2.ru/methods/test/.
The fact is that simply drinking vitamins (especially synthetic ones) is not effective enough if the basis for cell damage and nutritional deficiency remains.
I will not advise you to get tested, because the question said something completely different, I think the author realizes that there are no health problems. B vitamins are very good for the nervous system, they also improve memory and concentration. Or, even better - a multivitamin complex, selected depending on your age, occupation (physical activity). Oh, yes, even about the tests - if you are not sure, take a general blood test, you may have anemia (especially if you eat unbalanced), and some indicators may indicate latent inflammation (specifically leukocytes). Good luck and health :)
If you get tired regularly: you feel weak, tired or itchy in your bones, then I recommend getting tested for hidden infections, and in particular for chlamydia. And among vitamins for women, OptiWomen are optimal, and for men, OptiMen, respectively! But of course, one should not forget about at least minimal physical activity, such as: exercises, jogging, gymnastics.
At work - a blockage, at home, too, do not rest normally ... The head can not stand it.