And a last thing.
Cyclic forms of glucose are more stable than the linear form and thus, glucopyranose is (almost quantitatively) the main form in solid state. However, hemiacetal formation and hydrolysis are reversible reactions. Therefore there is equilibrium between all isomer forms in aqueous solution, due to the interconversion: glycopyranose ↔ linear form ↔ glucopyranose.
The composition of the isomers mixture is not constant but it depends on a variety of factors, such as concentration, pH, temperature, Hydrogen bonding, etc.
In other words:
When you drink a glass of glucose solution, the composition of the isomers mixture is different in the glass at room temperature, different in the empty stomach at 37oC and pH = 2-4, as well as different in blood at 37oC and pH = 7.35-7.45.