NHS use a range of 7.86 - 14.41 pmol/L when measuring t4. However, every time I've had a private test they use much higher reference ranges of roughly 12-22 pmol/L. Even weirder, my t4 always comes back much lower when NHS tested, and higher when privately. Therefore, it always comes back within range.
I know different labs use different ones, but my previous 5 tests have been:
15.5 (private, most recent)
8.9 (NHS)
9 (NHS)
9.5 (NHS)
9.4 (NHS)
16.2 (private)
15.8 (private, oldest)
They're the same unit of pmol/L. Just confused as my most recent private test of 15.5 would be classed as too high by the NHS range, and my previous 4 NHS tests would be classed as too low by the private range. Am i missing something?!
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katyy94x
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Hello, yep all done around 7:30am having fasted. None of these tests were done whilst taking levothyroxine, but i have literally just started it. Weirdly, my TSH was highest it's been when my t4 was 15.5. What might cause my t4 to naturally have improved whilst my TSH has gotten worse?
Waiting for my GP to come back to me about my vitamin levels at the moment.
Serum ferritin level is the biochemical test, which most reliably correlates with relative total body iron stores. In all people, a serum ferritin level of less than 30 micrograms/L confirms the diagnosis of iron deficiency.
Never supplement iron without doing full iron panel test for anaemia first and retest 3-4 times a year if self supplementing.
It’s possible to have low ferritin but high iron
Test early morning, only water to drink between waking and test. Avoid high iron rich dinner night before test
Eating iron rich foods like liver or liver pate once a week plus other red meat, pumpkin seeds and dark chocolate, plus daily orange juice or other vitamin C rich drink can help improve iron absorption
This is interesting because I have noticed that many patients with Hashimoto’s disease and hypothyroidism, start to feel worse when their ferritin drops below 80 and usually there is hair loss when it drops below 50.
Really interesting talk on YouTube, link in reply by Humanbean discussing iron deficiency and weight gain and towards end how inflammation can also be an issue
Thank you for your incredible patience while you have been awaiting the outcome of our ferritin reference range review. We conducted this with Inuvi lab, which has now changed the reference ranges to the following:
Females 18 ≤ age < 40. 30 to 180
Females 40 ≤ age < 50. 30 to 207
Females 50 ≤ age < 60. 30 to 264l
Females Age ≥ 60. 30 to 332
Males 18 ≤ age < 40 30 to 442
Males Age ≥ 40 30 to 518
The lower limits of 30 are by the NICE threshold of <30 for iron deficiency. Our review of Medichecks data has determined the upper limits. This retrospective study used a large dataset of blood test results from 25,425 healthy participants aged 18 to 97 over seven years. This is the most extensive study on ferritin reference ranges, and we hope to achieve journal publication so that these ranges can be applied more widely.
With serum B12 result below 500, (Or active B12 below 70) recommended to be taking a separate B12 supplement
A week later add a separate vitamin B Complex
Then once your serum B12 is over 500 (or Active B12 level has reached 70), you may be able to reduce then stop the B12 and just carry on with the B Complex.
If Vegetarian or vegan likely to need ongoing separate B12 few times a week
Thorne Basic B recommended vitamin B complex that contains folate, but they are large capsules. (You can tip powder out if can’t swallow capsule) Thorne can be difficult to find at reasonable price, should be around £20-£25. iherb.com often have in stock. Or try ebay
IMPORTANT......If you are taking vitamin B complex, or any supplements containing biotin, remember to stop these 7 days before ALL BLOOD TESTS , as biotin can falsely affect test results
In week before blood test, when you stop vitamin B complex, you might want to consider taking a separate folate supplement (eg Jarrow methyl folate 400mcg) and continue separate B12
Post discussing how biotin can affect test results
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Why do labs change reference ranges...?
Blood Reference Ranges
New reference range for TSH
Change in reference range
NICE thyroid reference ranges
