Radioactive iodine uptake

Alternative names:

iodine uptake test; RAIU

Normal values:

• 6 hours: 3 to 16%
• 24-hours: 8 to 25%

Note: Some laboratories only measure at 24-hours. There may be some variation in values with dietary iodine ingestion and with laboratory procedural differences.

What abnormal results mean:

Increased (greater than 50% at 24-hours is considered significantly elevated):

• hyperthyroidism
• Hashimoto's thyroiditis (early)
• hypoalbuminemia (low blood albumin levels)
• goiter

Decreased:

• hypothyroidism
• subacute thyroiditis
• iodine overload (excessive iodine ingestion)

See also "special considerations".

Additional conditions under which the test may be performed:

• colloid nodular goiter
• Graves' disease
• painless (silent) thyroiditis
• toxic nodular goiter