in the blood

They’ve been found in the blood, organs, and breast milk of humans.

Giving vitamin C through an IV produces very high levels in the blood, which cannot be achieved with oral delivery.

The test, which uses less than a quarter teaspoon of blood, works by stimulating the target T cells in the blood to release chemical signals, called cytokines, through which the quantity and quality of the target T cells can be measured.

Using their test, they assessed whether the engineered T cells remained in the blood and continued to function properly after infusion into the patient.

They point out there is another, more precise test and that only the more advanced test can definitively determine levels of insulin in the blood.