Vitamin B6 levels in blood after taking pyridoxine supplements
What it found
Taking 100 mg of vitamin B6 daily raised several forms of the vitamin in the blood of six people.
Rat liver cells in lab tests quickly changed added vitamin B6 into other forms and released them.
What they found
Studies in people
Blood levels rose in people
Before the supplement, total vitamin B6 forms in the blood averaged 114 nM. After one week of taking 100 mg daily, that average rose to 655 nM in the six subjects.
Main form stayed the same
One specific form called pyridoxal-P made up 54% of vitamin B6 in the blood before the supplement. It remained the most common form even after levels went up.
Levels steadied after one week
In three subjects who were tested weekly for three weeks, blood levels did not change much after the first week. This suggests the body reached a new balance quickly.
Animal and lab studies
Liver cells processed vitamin B6
Rat liver cells in lab tests changed added vitamin B6 into other forms within two hours. Out of 50 nmol added, about 21 nmol was turned into pyridoxal-P, pyridoxic acid, and pyridoxal outside the cells.
New vitamin B6 left cells fast
Freshly made pyridoxal-P inside the rat liver cells did not mix well with what was already there. Instead, it was quickly released or broken down into other forms.
What the authors conclude
- They conclude that vitamin B6 taken by mouth is quickly processed by the liver.
- The authors say the liver releases the vitamin into the blood mainly as pyridoxal-P, pyridoxal, and pyridoxic acid.
- They note that newly made vitamin B6 in liver cells does not mix freely with existing stores but is sent out rapidly.
How it was done
Scientists wanted to understand how different forms of vitamin B6 move through the body. The liver is the main organ that processes this vitamin, so they looked at both human blood and rat liver cells.
Six healthy adults took 100 mg of a vitamin B6 supplement by mouth each day for one to three weeks. Blood samples were taken before and during the supplement period. Separately, rat liver cells were kept in a dish with labeled vitamin B6 for two hours.
What it can’t tell you
- Only six people took part, so the results may not apply to everyone.
- The dose used was 100 mg per day, which is much higher than typical food amounts.
- Lab tests on rat liver cells cannot show exactly how a whole human body handles the vitamin.
The paper
- Title
- Plasma content of B6 vitamers and its relationship to hepatic vitamin B6 metabolism
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Lumeng L, Lui A, Li TK (1980). Plasma content of B6 vitamers and its relationship to hepatic vitamin B6 metabolism. The Journal of clinical investigation. doi:10.1172/JCI109906Free full textPubMed 7419716DOI
Summary written 30 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error