**Core Concept**
Unconjugated hyperbilirubinemia refers to an elevated level of unconjugated (indirect) bilirubin in the blood. This condition occurs when there is an imbalance between the production and clearance of bilirubin, leading to its accumulation in the bloodstream. Unconjugated bilirubin is a result of the breakdown of hemoglobin and other heme-containing proteins.

**Why the Correct Answer is Right**
The correct answer, **A. 85% of the total should be indirect**, is based on the normal distribution of bilirubin in the blood. In a healthy individual, approximately 85% of the total bilirubin is unconjugated (indirect), while the remaining 15% is conjugated (direct). This distribution is crucial for maintaining normal liver function and preventing the accumulation of toxic levels of bilirubin. The liver's ability to conjugate bilirubin is essential for its excretion into the bile.

**Why Each Wrong Option is Incorrect**

**Option B:** Hemolytic anemia is a condition characterized by the premature destruction of red blood cells, leading to an increase in unconjugated bilirubin. However, it is not a direct answer to the question and does not accurately describe the proportion of unconjugated bilirubin in the blood.

**Option C:** Haemoglobin destruction (bilirubin production) is a normal process that occurs when red blood cells are broken down. While it is true that bilirubin production increases in conditions of hemolysis, this option does not address the specific distribution of bilirubin in the blood.

**Option D:** 50% of the total should be indirect is an incorrect statement, as the normal distribution of bilirubin in the blood is approximately 85% indirect and 15% direct.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that unconjugated hyperbilirubinemia can be caused by a variety of factors, including hemolysis, liver dysfunction, and certain medications. The distribution of bilirubin in the blood can provide valuable clues about the underlying cause of hyperbilirubinemia.

**✓ Correct Answer: A. 85% of the total should be indirect**