Why is a first-morning urine sample required for a urine HCG test?

Generally, the main reasons for using first-morning urine for urine hCG testing include higher hCG concentration in morning urine, nocturnal urine concentration, interference from urinary tract infections, influence of medications on test results, and hormonal fluctuations during early pregnancy. If test results are abnormal, it is recommended to promptly visit a regular hospital for further confirmation. Detailed explanations are as follows:

1. Higher hCG Concentration in Morning Urine

After a night's sleep, urine remains in the bladder for a longer period and hCG is not excessively diluted, resulting in a relatively higher concentration that improves test accuracy. Avoid drinking large amounts of water at night before the test to maintain natural urine concentration.

2. Nocturnal Urine Concentration

During the night, the body's metabolic activity slows down and urine is produced more slowly. The solute components in urine are less likely to be diluted, allowing hCG concentrations to remain stable. Avoid drinking water 1–2 hours before bedtime the previous night to ensure effective urine concentration.

3. Urinary Tract Infections Affecting Testing

When suffering from urinary tract infections such as urethritis or cystitis, bacteria or inflammatory secretions may be present in the urine, which can interfere with hCG test results. Under a doctor's guidance, medications such as cefaclor capsules, levofloxacin hydrochloride capsules, or amoxicillin capsules can be used to treat the infection, after which testing can be performed once the infection has resolved.

4. Medications Interfering with Test Results

Certain hormonal medications may affect the accuracy of urine hCG testing, potentially causing false-positive or false-negative results. If testing is required, inform your doctor about any medications you are currently taking. When necessary, discontinue the medication for a period under medical supervision before undergoing testing.

5. Hormonal Fluctuations in Early Pregnancy

In early pregnancy, hCG levels are relatively low and fluctuate greatly. During the day, factors such as water intake and frequent urination may reduce hCG concentration in the urine, affecting test accuracy. Morning urine testing can reduce errors caused by hormonal fluctuations. If the result is questionable, repeat the test after 1–2 days.

Prior to testing, avoid excessive water intake and maintain a normal diet. Follow the test instructions carefully to ensure correct testing procedures. If there are doubts about the test results, promptly visit a hospital for further tests such as serum hCG testing to confirm the diagnosis.