Thyroid UK
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New here - not sure whether to start medication

I would like some advice. I am a 66-year-old man. Because I suffer from enlarged prostate, I have an annual blood test to check my PSA levels, and this year my thyroid came up as slightly outside the normal parameters.The serum free T4 reading was 8.5 pmol/L and the serum TSH 5.47 mu/L.

My doctor has suggested me starting on levothyroxin 25 µg.

The only symptom I have that seems to me to be possibly thyroid related is unusual levels of tiredness, which I have had a problem with for some time. Having to get up usually 2 to 4 times per night to go to the toilet does not help. I have no weight gain, and no noticeable other thyroid symptoms.

I am not sure whether to start on this medication or not. I already take 400 mg tamsulosin (Flomax) for my prostate issue which I've been on for a number of years, and I'm not keen to start on any other medication as well unless I'm confident it's going to be helpful. Can anybody advise me?

4 Replies

Welcome to the forum, jd2387.

Do you have the lab ref range for FT4 (the figures in brackets after the result)?

Why not take the Levothyroxine and see whether it improves fatigue? It takes 7-10 days for Levothyroxine to be absorbed before it starts working and it will take up to six weeks to feel the full impact of the dose. Symptoms may lag behind good biochemistry by several months.

For maximum absorption Levothyroxine should be taken with water 1 hour before, or 2 hours after, food and drink, 2 hours away from other medication and supplements, and 4 hours away from calcium, iron, vitamin D supplements, magnesium and oestrogen.

You should have a follow up thyroid test 6-8 weeks after starting Levothyroxine as 25mcg is a starting dose and may not be sufficient. Arrange an early morning and fasting (water only) blood draw when TSH is highest, and take Levothyroxine after your blood draw.


Thanks for your response. The lab range for Serum free T4 is 9.00 - 19.00 pmo/L.



FT4 is blow range and ideally should be in the upper range so you should take the 25mcg Levothyroxine. Fatigue will almost certainly increase as your FT4 drops further without Levothyroxine replacement and you may develop other symptoms which you have been lucky not to experience yet.




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