Is blood cholesterol supposed to be always the same level or there are variations according to the age?
Levels generally increase until the ages of 50-60, then fall.
In children, levels of LDL and HDL generally either rise or fall monotonically (i.e. continuously) over childhood; see Dai et al. (2009). LDL-C was found to decrease in both genders, while HDL-C was found to increase in girls and fluctuate in boys.
Blood cholesterol begins to rise around age 20 and continues to go up until about age 60 or 65. Before age 50, men’s total cholesterol levels tend to be higher than those of women of the same age—after age 50, the opposite happens. That’s because with menopause, women’s LDL levels often rise.
After about the age of 50, both men and women generally experience a fall in blood cholesterol levels (see Ferrara et al. (1997)).
Additionally, levels in all age groups may fluctuate according to the seasons (see Ockene et al. (2004) and cited studies therein). However, the reason for this is unknown.