Is my increased mileage effecting my Levothyroxine dosage?

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20/05/2013 at 16:38

I was diagnosed with hypothyroidism about 4 years ago after some very unpleasant illnesses which pretty much curtailed my training. I've been on levothyroxine ever since with blood tests every 6 months. Last September I completed my first marathon for 10 years. Since then I have cut back my training to pre marathon levels, and continued with my 3 weekly hard core aerobics classes, My speeds have gone up and I'm feeling great. BUT, I've been losing a lot of weight, my hair is falling out, and I'm not sleeping well. I've got another blood test booked in a couple of weeks, but I wondered if anyone had an opinion on whether my exrecise level is making me need a lower dose of levothyroxine. Has anyone tried varying their dosage to take into account their increased/decreased activity level?

20/05/2013 at 19:26

Say you need a blood test now for the reasons you have given. Say you want it fast-tracked with an early appointment with your G.P. to discuss blood results and your general health.

Do not adjust your dosage of levothyroxine (up or down) without your doctor's instruction. I cannot believe you have even thought about it  "after some very unpleasant illnesses".

20/05/2013 at 22:58

Thanks for your comments, Martenkay. Actually it was a doctor who suggested varying the dosage according to activity level. I wasn't planning on going ahead without consulting a doctor, I am just interested if anyone else has experienced the same symptoms as this. There is anecdotal evidence that more exercise = more naturally produced thyroxine, but I haven't seen anything from runners, as yet. I like to be as well informed as possible before I see my doctor. After all he/she isn't a runner......

20/05/2013 at 23:03

I've never heard of anyone varying their dosage depending on activity level, and I can't begin to think how it might work - levothyroxine has a half life of about a week, and it takes several weeks after commencing a dose for plasma levels to settle. So to think that day to day activity should require a variable dose just makes no sense to me.

21/05/2013 at 07:46

I know that when I'm in hard training my TSH is suppressed - but I don't vary my thyroxine levels as it usually goes back up within a couple of weeks of easing back - and I've never been (possibly) symptomatic of being hyper.

21/05/2013 at 17:09

I have been right on the borderline of dosage, they could not get exact dosage due to tablet sizes, but GP said to take the higher dose for at least a month, if any symptoms to cut back and speak to him again then monitor it for another 3 months. As it was I stayed on the higher dose with no side effects.

I have never heard of varying the amount required due to increase in actrivity, if your thyroid is not producing enough stuff naturally no amount of exercise is going to increase what it produces.

I even asked about taking the pills late at night to not interfere with a really early start time for a race, emphatic answer was NO. Take it in the morning 30 minutes before food and mug of tea. So I woke up at 3.15am to take tablets.

Edited for spelling errors.

Edited: 21/05/2013 at 17:12
22/05/2013 at 15:19

I managed to get a blood test today and an appointment with the doc on Tuesday. I'll update this thread some time next week.

01/06/2013 at 23:14

Hi cjbv how did you get on at the doctors? Hope you got sorted.

02/06/2013 at 07:53

Blood test done and visit to Doctor over. The results were as expected - my dose ws too high and all these symptoms were related to that. I'm expecting to lose the overdose symptoms in about 3 weeks and go back for another blood test after 6 weeks.

I  chose a doctor with a particular interest in thyroid problems and she told me that my exercise level will definitely be affecting my thyroid levels.I didn't ask her about varying the dose according to exercise levels, but I'm going to keep a record of symptom chjanges and see if I can spot a relationship myself. I guess that is going to take quite some time!

Thanks for everyone's comments and I hope this discussion is useful to many people. 

02/06/2013 at 09:01

Glad to hear you're sorted. I wouldn't vary the dose according to exercise as that would be very difficult to judge on a week to week basis but I would be aware that if you enter a period of hard training and your TSH is already on the low side that may push you into being hyper, the lowest I've been tested at is 0.1 - but as I wasn't symptomatic we just left the dose as was, retested about two weeks after my race and found that it had returned to closer to 2 - so no need to change the meds at all.

Steady - given the half life of thyroxine I think your doctor was being a little pedantic saying that you couldn't take your dose the night before - in fact there's some research supporting taking it before bed rather than in the morning


02/06/2013 at 20:21

Good to see that your doctor quickly identified your problem. Your symptoms were typical of too high a dose. You might have saved your eyebrows! What you will probably soon find is that your weight will go back to normal and you will begin to sleep better and generally feel better..

Obviously I know nothing of your running but it is likely that you will also see some falling away of speed or having to work much harder to maintain levels reached. Yes, you've been having some assistance!

03/08/2013 at 20:00

Just want to join this thread. My annual follow up has indicated I might have hypothyroidism. They're tracking me for a bunch of illnesses that are common following radiotherapy and chemotherapy.

My haematologist has suggested a retest. I have to talk to my doctor on Monday. Would marathon training/overtraining cause false readings. 

My blood test was done 3 days after a half marathon PB on a hot day and a hard course.

Obviously I'll go for a retest but am now training for a September marathon.

My only symptoms are tiredness and sore skin, which on their own I heven't taken much notice of. 

03/08/2013 at 21:26

TimR, I only had 3 symptoms - extreme tiredness, dry skin and my periods went haywire, so it is possible.
You are sensible in having a retest, so long as you are not overtraining at the moment for your marathon I would have thought the next blood test would be more representative of the hormone levels.

Thanks for the link Little Miss Happy, it was the pharmacist who made the comment, I will not worry next time I have such an early race start.

04/08/2013 at 06:17

Hi Tim, I wouldn't expect marathon training alone to make much of a difference to your TSH or T4 readings but there is little research on the subject. I have to be training consistently around 12 - 15 hours a week for it to affect my results.

Glad to be of help Steady - it's bad enough without inconveniences like that!

04/08/2013 at 17:37

Thanks for your input. I ran 14miles this morning and struggled. It was hot but I've had no energy this afternoon at all. I'll report back soon. 

26/09/2013 at 12:57

Soonish then. Marathon completed on Sunday and went to see doc this morning. Second test confirms hypothyroidism. Now have a prescription so let's see how I go from here.

Any tips?

26/09/2013 at 15:49

Just keep taking the tablets.

26/09/2013 at 16:09

As above!

And just to add in - I always take my tablets in the evening and my bloods have been stable for years

26/09/2013 at 16:12

You may need to pace yourself for a while - I found working to HR helped me as it stopped me beating myself up over being slower and also meant that I could keep the distances up easier. Once you have your meds sorted though there's no excuses - I've PBd at all distances and do IM triathlons with reasonable success

26/09/2013 at 21:03

Will I slow down when I start taking them or just stay the same and notice an improvement in 3-4 weeks? 

I generally run to HR on 13mile plus runs anyway. 

I have a 10mile race in October and planning a PB half marathon in November. 


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