PTU dosage question: Hi I’ve been on PTU 200mg... - Thyroid UK

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PTU dosage question

Chi68 profile image


I’ve been on PTU 200mg daily for 6 weeks now and had a blood test this week.

TSH < 0.01 (0.35 - (5.00)

T4 13.2 (9.0 - 21.0)

6 weeks ago my T4 was 22.7 after 5 weeks of 20mg carbimazole

When I called for the result of the blood test I was told it was normal. I asked to speak to my GP to ask if my dose needed reduced. She did call me back and I was told to carry on taking 200mg and recheck thyroid function in 8 weeks. She said they may add levothyroxine after my next blood test? I was referred to an endocrinologist at the end of September but not heard from them yet.

Does this sound normal? From what I’ve read I thought the PTU dose would be reduced as I’m euthyroid?

16 Replies

Yes you are right. The anti - thyroid medication works by lowering the amount produced (not the existing level). So you can see by your results the current dose has successfully reduced the level.

Stay on same dose the drop will continue. The “feed” needs adjustment or the “tank level” will drop. You need to be kept in range. Often the dose is halved but you may do better if reduce by quarter 50mg. Do you have another test scheduled?

GPs do not usually manage hyperthyroid treatment and monitoring it requires a specialist. And many of them are not adept as they should be as they look purely at TSH and want to see it to rise into range and allowing your FT4 & FT3 To drop below range would achieve it faster. Although you may feel very unwell before the TSH responds.

Chi68 profile image
Chi68 in reply to PurpleNails

Thanks for replying. I thought that was the case, I don’t want to become hypothyroid. I’m tempted to half the dose to 100mg. She asked me to get my blood checked in 8 weeks and I’m pretty sure I’d be hypo by then if I continue taking 200mg daily

Hey there again ;

Some endocrinologist offer the patient Block and Replace treatment :

The patient is kept on a high dose of the AT drug and T4 - Levothyroxine is added back into the medication to be prescribed :

In this way, by having a measured dose of T4 each day you should not " fall too far " into the lower end of the ranges thereby not having to experience symptoms on hypothyroidism.

It's a fine line and takes great skill to get the medication right when you are in this first phase of the disease so keep notes of symptoms at every dose so you can give feedback rather than just being a mathematical equation on the computer.

It's also important for you to be heard and feel involved in the decisions being made.

Chi68 profile image
Chi68 in reply to pennyannie

Thanks. I’ve not seen an endocrinologist yet. My GP is wanting me to stay on 200mg for another 8 weeks then retest. She said they may start levothyroxine after my next blood test

pennyannie profile image
pennyannie in reply to Chi68

Yes, I understand but think your doctor is taking instruction as to your medication needs through advice from the hospital endocrinology department.

Chi68 profile image
Chi68 in reply to pennyannie

No, she asked if I had an appointment yet then said they’ve not heard anything since asking advice when I couldn’t take carbimazole

pennyannie profile image
pennyannie in reply to Chi68

OK then :

Hi. I have graves and take PTU like yourself.

The 200mg dose is doing the job of reducing the levels. What is not seen is where your T3 is.

Your T4 is 13.2, how do u feel?

If you continue the 200mg dose u will end up hypo that is a guarantee.

The adjustment of the PTU would be to go from 200mg at 13.2 to 100mg and retest in 4 weeks.

200mg is an aggressive dose and will render u hypo.

100mg is a chance to see how effective the dose is at holding the T4 at 13.2.

My personal opinion for what it is worth. How do U feel most importantly? Do u need my T4? And I feel that you cannot reasonably answer that question because T3 has not been tested.

Chi68 profile image
Chi68 in reply to NIKEGIRL

Thanks for replying. I’m feeling pretty good just now. Heart rate is back to normal and no longer shaky. T3 can’t have been checked. I’ve got a copy of the result and only TSH and T4 are on there.

I don’t think the GP will recheck my blood in 4 weeks….I had to insist on this test after 6 weeks on PTU and she said recheck in 8 weeks.

NIKEGIRL profile image
NIKEGIRL in reply to Chi68

Ok. So with no T3 being checked then your choices are based on:

1 How do u feel?

2 How do I feel at the top end of the range and does being at the top end give any physical or emotional symptoms?

Personally I would want to be at the top of the range to then give room for exercise to burn up some T4.

If u continue at 200mgs u will end until hypo. Fact

Now it’s time if u chose to experiment at 100mg or even at 50mg to bring the T4 up.

What I am going to say is. I am T3 dominant and I represent 20% of graves patients. So in basic language what that means is T4 is in range and T3 is well over.

With u not getting T3 tested u will never know this but also having said that your tremor has gone and heart is better which suggests T3 is ok but u don’t have any factual numbers to confirm that

NikeGirl makes an excellent point. Your Doctor (likely looking at just the TSH) also doesn’t have a FT3 result to check. It can’t be assumed that if FT4 is in range FT3 isn’t disproportionately under or over. Especially with Graves which can cause erratic surges or cause deficient nutrients which would reduce conversion.

You need to be extremely careful if self adjusting. Make the adjustment small and don’t alter too much without regular retesting.

It’s not an effective approach to alter by how you feel. You could think you feel well assume your levels are under control and decrease dose, but miscalculate your levels could rise. Adjustments can take over 6 weeks to manifest & find new level so many adjustments won’t help you.

I started on 20mg carbimazole, after 8 weeks my levels were approaching hypo the dose was halved and propranolol stopped. I mention propranolol as it effects FT4:FT3 conversation, & shouldn’t be ceased abruptly. 6 weeks later the FT3 was over range so was adjusted to 15mg. Then I went through a stage of levels rising & dropping with dose changed to 15mg daily to 10mg daily. I didn’t feel well with levels being altered even though I was mostly within range. It didn’t settle until I suggested 15mg alternating with 10mg. When I lost weight, that also started lowering my thyroid levels but instead of dropping dose in a chunk they agreed I could adjust down smaller which worked out much better. I find if I adjust more that 2.5mg carbimazole per day increase or decrease I do not feel well. I have never been horrendously hyper or hypo so my adjustments have always been about fine tuning.

When hypothyroid the replacement is increased or decreased slowly by 25mcg a day, retesting after 6 weeks, yet when hyper the approach is halt high levels immediately and then allow rises quickly.

As hyper is dangerous there is a logic to reducing swiftly but allowing quick rises may not help you either.

Gradual adjustments may help you in the long run. Definitely don’t be tempted to adjust daily on how you feel.

Hello purple nails are you still on drugs or back to normal?

Still take low dose carbimazole. I have a nodule so no possibility of remission as not autoimmune. What about you? Do you have hyperthyroid condition?

I was just recently diagnosed with hyperthyroidism scan shows tiny nodules 3weeks ago ,I'm on carbimazole 20mg and I trust God to be fine. I pray you get well soon

Nodules do not always overproduce. An ultrasound can’t determine function but an specialised uptake scan does. This is usually done to confirm when hot or toxic nodule/s are suspected. Antibodies should also be tested to rule out autoimmune. If you do your own post members can offer advice for you.

Thank you so much

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