Can blood test with have different results depending on time of day they are taken?

1 answer | Last updated: Sep 30, 2016
A fellow caregiver asked...

Mom has Alzheimer's 82. No short term memory but is still functional but confused. Her thyroid T4 was fine a year ago but blood was drawn during the day when she had more energy. Had blood drawn again a year later early am no food and now her thyroid T4 is considered high 6.10 though T3 was fine. Can a blood test with thyroid differ in results as to when its taken? (AM or PM) or is a test a test? How can a thyroid go to Hypo within a year. Plus having problems getting her to take her pills she is not a pill person. When she did take them she seemed more energetic but in a way maybe too much so I wonder if she's really HYPO. Dr said her thyroid is getting old. Should Thyroid reading be the same no matter when its taken?


Expert Answers

Jennifer Serafin, N.P. is a registered nurse and geriatric nurse practitioner at the Jewish Homes for the Aged in San Francisco.

Regarding your question about thyroid testing: Unlike some other lab tests, thyroid tests are not time sensitive. So, it does not matter what time of day you take a thyroid test, since the hormone levels will not fluctuate that much.

It is very possible to go hypo/hyperthyroid in a year. I have seen people thyroid function change in as little as one month, especially if they are ill.

My recommendation is to get her to take the thyroid medication every day, as untreated hypothyroidism will eventually affect your mother's health, and may worsen her memory problems. Good luck!