Pyridoxal-5'-phosphate (P5P) is the biologically active form of vitamin B6 that is utilized by the body. Studies show that for people with compromised liver function, P5P is 3 times more likely to be absorbed than conventional B6. Inadequate levels of plasma P5P can lead to anemia, depression, dermatitis, hypertension, water retention, insomnia, premenstrual tension, irritability, muscle twitching, convulsions, and kidney stones.