This product contains 5-MTHF, also known as Quatrefolic. Unlike the glucosamine salt variant ("folic acid"), this is absorbed very efficiently and can be used directly by the body. The glucosamine salt variant must first be converted by the body into the active form.

It concerns a dosage of 500 mcg. This has no impact on blood sugar levels and no interaction with vitamin K.

Other forms of folic acid also have no interactions or side effects at this dosage.

The reports you have read pertain to mega-doses of folate, such as 5000 mcg, which is ten times what is in this capsule. Such dosages are only used for specific therapeutic purposes, typically in combination with vitamin B6 and betaine.

Dosages between 400 and 800 micrograms of folic acid/folate per day can be considered a mild maintenance dosage. Such dosages are also present in most multivitamins.

The ratio between vitamin B12 and folic acid/folate is not important. It is not the case that if you take twice as much B12, you need to take twice as much folic acid. In fact, it is not even necessary to supplement with folic acid if you are already receiving sufficient folate from (leafy) vegetables. However, on the other hand, there is nothing wrong with using a combination product. What the body does not need is effortlessly excreted.

The Bonusan Co-Enzyme B12 1500 mcg is not in the form of a lozenge. When B12 is taken in the form of methylcobalamin and/or adenosylcobalamin, a lozenge is not really necessary, as these two forms of B12 are also well absorbed in the stomach, unlike the "old-fashioned" form of cyanocobalamin, which is indeed best administered in the form of a lozenge. The downside of a lozenge is that it requires more excipients (including sweeteners and flavourings) and is therefore also more expensive than a compact tablet that can be swallowed.