With testosterone cypionate levels provided by injection will drop by about half in about a week or a little less. So in four weeks, only about 1/16th will remain.
Let's say you were taking 100 mg/week (you did not say.) If so, your blood test might be increased by an amount similar to if you were injecting not 100 mg/week, but about 1/16th of that or less, or about 6 mg/week. Which would be small enough to be of no concern to the accuracy.
Because of variability, the actual result could be a little different, not exactly like "6 mg/week," but would still be low enough to not affect accuracy at all importantly.