Time of day for thyroid testing

[VitaminB12]

Do you go for thyroid testing in the morning or the afternoon? I work in the morning so I need to go in the afternoon.
Recently I read online that a ND recommended morning not afternoon bloodwork due to regular flunctations in hormone levels.

[VitaminB12]

Thanks for your post. I had my bloodwork done this morning. I will post the results once I receive them.

[Barb135]

Exercise builds muscle, which burns fat and helps boost metabolism, but a walk to the lab isn't going to change your thyroid levels...  If your thyroid isn't producing hormones, exercising isn't going to make it start producing them.

[VitaminB12]

Thanks for your post. I thought exercise was recommended for those with an underactive thyroid to boost metabolism.

[Barb135]

To my knowledge exercise does not have that much immediate effect on thyroid hormone levels, so you walk to the lab should not change your results.

[VitaminB12]

I plan on going for bloodwork July 24 am. I've arranged to arrive late to work.

[VitaminB12]

So, you don't think a half hour walk will have any significant affect on my thyroid results? I walk at a good pace.

[VitaminB12]

Thanks for your note.

[Barb135]

If I could walk to get my labs done, I'd love it... I could probably walk it in 1/2 hr, but the terrain and traffic are so unfriendly/dangerous - I'd be lucky to get there at all.

[VitaminB12]

Thanks for your post. The lab I go to opens at 8 am and it's a half hour walk from home.

[Barb135]

I always get my blood work done first thing in the morning, even if I don't have to be fasting.  The only difference with thyroid labs is that I can have coffee, and maybe a bite to eat first...  The lab I go to opens at 7:00 am, so I can get in and get it done early, take my T3 med right after the blood draw, then go on with my day, as usual.

[VitaminB12]

What time of day do you typically go for thyroid testing if you do not need to fast for other tests?

[VitaminB12]

Thank you for your post.
I'm pleased that my doctor has offered to test my thyroid again (TSH, Free T4, Free T3) when I recently went to see him to request ferretin/iron test. He will also have my B12 checked again as well as blood. A side effect of the B12 supplementation is a slight change in my hematology. It does state right on the bottle that it "helps produce red blood cells." That is not why I am taking it though. It's because I am vegetarian and don't get enough through my diet even though I include some dairy (yogurt/kefir) and eggs (hard-boiled).

May 2, 2014 lab results
Hematology
RBC Indices: MCV 102 with reference range F: 80 -99 fl
                    MCH 35 with reference range 27 - 32 pg

[VitaminB12]

Thanks for the info! In order to fast and have the test done first thing in the morning I would have to request to start work late. I have requested to do this at least once since being in my current job so I figure I should be able to ask again. It was for a glucose test.

[Barb135]

Thyroid labs do not have to be fasting, though if one is taking T3 thyroid med, it should not be taken prior to the blood draw.  I always take my T4 prior to blood draw because what's in my blood is what I took a couple weeks ago.

I often end up having other labs at the same time that do require fasting, such as the lipids or CBC, BMP, including fasting glucose .. those should be done first thing in the morning, when truly fasting.  Fasting involves nothing to eat/drink for 8 hrs, other than water... You should always make sure you are well hydrated when you have blood drawn, at whatever time of day...

[jacrjacr]

I have found that if I fast from 12 midnight until the next morming and no caffeine until after test, my test seem to be more accurate to the way I am feeling so I started doing that. I just drink water until my test and try to take it before 9am too

[VitaminB12]

Interesting. I eat unless I am requested to fast.

[Red_Star]

It's based on the various studies I've read. I meant 8 - 9 am. The study was based on 8 - 9 am and 2 - 4 pm. I'll fast for all tests unless it states I have to eat something first.

[VitaminB12]

Thanks for your post. Now that I know time of day matters I can see a pattern in my results. Due to work schedules and other commitments I have not been able to get to the lab for bloodwork at the same time or even the same time frame each visit. So I have morning and afternoon readings. The morning TSH levels are significantly higher than the afternoon ones.

[VitaminB12]

Were you advised to fast or is this just your preference?

[Red_Star]

That last quote seems a bit conflicting to the study lol. Anyway, I always have my thyroid labs done between 7 - 9 am in the morning on an empty stomach.

[Red_Star]

Natural Medical Journal - Thyroid-stimulating Hormone Fluctuates With Time of Day - Time of day matters when drawing blood for diagnosis...

"TSH levels were lower in the afternoon compared to morning values in 41 of the 42 participants. Median TSH in the subclinical hypothyroid group was 5.83 mU/L in the morning vs 3.79 mU/L in the afternoon (P<0.001). Median TSH in the primary hypothyroid group taking L-thyroxine was 3.27 mU/L in the morning vs 2.18 mU/L in the afternoon (P<0.001) Using the current reference range of TSH (0.4–4.0 mU/L), an afternoon blood sample would lead to a missed diagnosis in 50% of those with subclinical hypothyroidism (P<0.0001). Per participant, the range of TSH variability reached highs of 73% in the SH group and 64.7% in the PH group.

Practice Implications

That there is a circadian rhythm to thyroid hormones is not surprising as the hormonal milieu is associated with diurnal rhythms. Thirty-five years ago, fluctuating TSH levels were demonstrated and found to be at their highest in the middle of the night.1 Current research suggests that TSH serum levels peak at between 2 am and 4 am and decrease to their lowest levels at between 4 pm and 8 pm.2 Thus, the lower afternoon TSH levels found in the current abstract are consistent with previous research."

"A diagnosis could be missed in 3 out of every 10 patients with subclinical hypothyroidism if the blood draw is done later in the day."