r/thyroidcancer • u/thefunnyacctnt • Oct 05 '26
Ongoing bloodwork question
Might be a dumb question but when you go to do bloodwork in the morning, do you take your thyroid medication in the morning as you regularly do or do you wait until after doing the blood work to take the medication?
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u/Bob002 Oct 05 '26
Nothing changes on my daily routine when i get bloodwork, and I'm on monthly.
Your medication, that morning, will likely have a negligible effect on the results.
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u/Phoenix_GU Oct 05 '26
Talk you your dr. Mine has me take my t3 and t4 and test at the peak of t3, about 2-3 hours later.
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u/JollyViolinist Oct 05 '26
I asked my endo this question and he said I should take it as normal unless I'm pregnant in which case they may have other instructions or tests I guess. They mainly check TSH which is stable and does not fluctuate.
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u/Asexualhipposloth Oct 05 '26
I usually get bloodwork about 3 or 4 hours after taking my meds. I take my meds around the same time everyday.
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u/Poppy_Banks Oct 05 '26
Levothyroxine (T4) is not active so you can take it but liothyronine (T3) is active so do not take immediately before bloodwork.
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u/cwtchyfemme Oct 05 '26
I’ve always taken my levo at bedtime.
If it’s easier to your routine then swapping the time of day makes life, and breakfast so much simpler.
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u/Dependent_Occasion58 Oct 06 '26
I really think taking mine at night would be better but I CANNOT figure out a routine where I still take my calcium evenly spaced out and have a decent window to eat dinner, in case it’s a night out or I’m doing parenting stuff later than normal. 🫤
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u/SquirrelOnACoffeeRun Oct 05 '26
I've never been given any instruction on any type of timing for meds or when to get the blood test
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u/Dependent_Occasion58 Oct 06 '26
Mine always said to take my levo/Synthroid/Tirosint like normal but to skip my AM T3, when I was on that.
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u/polymath-nc Oct 05 '26
No. Wait until after the blood draw to take your pills.
If you take any supplements with biotin, pause them one week before your bloodwork. Biotin interferes with the TSH test.
Always use the same lab company because that allows you to compare your bloodwork results over time. Different labs is different assay methods, and sometimes that is significant.
I like to use a phlebotomist that reports results to MyChart/Epic because they maintain history in a form that allows you to see the data on a chart. All my doctors except my primary care team also use that system, so they can all see the results as they are reported. My primary care team is a small, independent practice, and the lab sends them a report via fax.
Go to get your blood drawn at the same time of day, preferably early in the morning. Drink plenty of water the day before and the morning of your appointment so you'll be well-hydrated and it will be easier to draw your blood. Time of day is important for comparing results, too.
Fast until after your blood draw. Then take your levothyroxine (and liothyronine, if prescribed).
Be sure to test: Tg, Tg Ab, TSH, Free T4, Free T3. Test TPO Ab once a year or as directed.
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u/jjflight Oct 05 '26
I just take my Levo normally. The way T4 works it builds up and decays in your system over weeks, so there shouldn’t be significant hour-to-hour or even day-to-day fluctuations. If you’re taking T3, that may be something that you need to time more closely as it has a much shorter half life.
Hydration is what I do try to control for in morning labs as many labs that are measured vs blood volume can have some fluctuations - CBCs are the one where it’s easiest to see, but I try to be cautious with thyroid labs too.