Labs how to do blood tests?

[kikiweight]

I’ve had thyroid labs done several times over the last few years and no one ever tells me to fast, not take meds etc. Even the two endo I’ve seen. What are the best times to take tests and what should I request?

I’ve had ongoing hypo symptoms for approx 2 years now. All ‘normal’ labs but am on NT after begging a skeptical endo to let me try it. So far, some improvement but I still don’t feel right- a non stop sore throat for one- and I continue to gain weight.

[SeasideSusie Remembering]

kikiweight

When doing thyroid tests, we advise:

* Book the first appointment of the morning, or with private tests at home no later than 9am. This is because TSH is highest early morning and lowers throughout the day. If we are looking for a diagnosis of hypothyroidism, or looking for an increase in dose or to avoid a reduction then we need TSH to be as high as possible.

* Fast overnight - have your evening meal/supper as normal the night before but delay breakfast on the day of the test and drink water only until after the blood draw. Eating may lower TSH, coffee affects TSH so it's possible that other caffeine containing drinks may also affect TSH.

* If taking thyroid hormone replacement, last dose of Levo should be 24 hours before blood draw, if taking NDT or T3 then last dose should be 8-12 hours before blood draw. Split the dose if necessary/adjust timing the day before if necessary. This avoids measuring hormone levels at their peak after ingestion of hormone replacement. Take your thyroid meds after the blood draw. Taking your dose too close to the blood draw will give false high results, leaving any longer gap will give false low results.

* If you take Biotin or a B Complex containing Biotin (B7), leave this off for 7 days before any blood test. This is because if Biotin is used in the testing procedure it can give false results (most labs use Biotin in the assay).

These are patient to patient tips which we don't discuss with doctors or phlebotomists.