Dosing by weight for levothyroxine

[Sailing14]

Woukd anyone be able to confirm if dosing by weight is accurate? And if so, can other factors affect this?

Thank you

[helvella Administrator Thyroid UK]

On the contrary, I can confirm it is NOT accurate!

We know that some members are on what appear to be ludicrously high doses. Seemingly because they do not absorb oral levothyroxine adequately. This is also very extensively documented.

At the other end of the scale, switching from a tablet to an oral solution or gel capsule (Tirosint) has been widely documented as possibly increasing absorption by a substantial percentage (e.g. 10 to 25% seems feasible). Yet none of the dose-by-weight guidance I have seen suggests any different dosing rate for these products.

At best, it suggests what dose someone MIGHT need.

The primary work on dose-by-weight seemed focussed on post-thyroidectomy treatment. Where someone has a working thyroid which is removed due to goitre or cancer. And they need to suddenly start replacement thyroid hormone therapy. There is no sense or need to see them become profoundly hypothyroid then slowly titrate. Go for best guess then adjust.

If already hypothyroid, suddenly delivering a full dose is unlikely to be a good experience.

helvella's calculation document and spreadsheet can be can be found by following this link:

helvella - Estimation of Levothyroxine Dosing in Adults

A discussion about the use of formulas to estimate levothyroxine dosing. Includes link to a downloadable spreadsheet which calculates several of these.

helvella.blogspot.com/p/hel...

[Sailing14 in reply to helvella]

Thank you helvella and for your informative post. I have to agree and that it is predominantly absorption issues for us.

[Lulu2607]

I'm not sure the dosing by weight is completely accurate. I think dose depends on a number of factors and will vary depending on your symptoms, general health and other co morbidities etc. personal to yourself. My dose has varied since being diagnosed severe hypothyroid, autoimmune cause , TSH 162 a few years ago and currently is lower than you'd expect if you applied the weight/dose rule but I feel OK. Maybe use as a general guide but I don't think it's a clinical tool that's applied by medics to determine your dose.

[Sailing14 in reply to Lulu2607]

Thank you. Yes I will consider all these things. My weight has increased by around 10 pounds since September so I feel it could be correct that I need a further increase (but only very small). Although, I have other problems with my health too but the thyroid is at the centre of everything as we know.

[Lulu2607 in reply to Sailing14]

With regard to weight, I have found that an increase in dose is not effective if your Iron, vit D etc are under par. I was able to lose/maintain weight when my levo was slightly reduced but I'd managed to improve my iron and vitamin levels. I imagine it makes the levo more effective. I had been under huge stress due to personal events and had neglected my health, not eating properly etc but improving nutrients alongside the correct levo dose is very effective. No amount of levo will help your symptoms if your health is under par. It takes a good while to improve things and a lot of focus but it's worth it.

[helvella Administrator Thyroid UK in reply to Lulu2607]

You are right to point this out.

If we imagine someone low in iron, B12, folate, vitamin D - and yet they somehow have apparently good thyroid hormone levels despite these issues. If they now address all these other issues, they could end up feeling over-medicated.

[Sailing14 in reply to Lulu2607]

Thank you. This is all very true. I feel mine is also to do with medication and infection and it depleting essential vitamins (although mine are in range), but not were they need to be to maintain our thyroid health.

Thankfully, I can go to this forum for help as the medical profession dismiss through lack of experience and suffering this condition themselves.

I think you have to have this disease to fully know as we are aware.

[Sparklingsunshine]

Its probably no more than an inkling or rough suggestion. My dose has varied between 150mcg and upto 200mcg, but at no point was I overmedicated and I'm a normal weight. I suspect I have absorption issues as I have a long history of deficiencies of iron, folate, B12 and Vitamin D.

I take Levo in the early hours with just water so am doing everything possible to aid absorption. Some of us dont take in as much as we should.

[Sailing14 in reply to Sparklingsunshine]

Thank you. I agree with you on the absorption issues due to my IBS and lactose intolerance but I have increased weight too as noted above so will have to look at a small increase.

Well done for all your efforts when dealing with this forgotten illness.

[SlowDragon Administrator in reply to Sailing14]

Are you on lactose free levothyroxine

[Sailing14 in reply to SlowDragon]

I avoid lactose food and drink but I didn’t get on with Aristo so I have to try the liquid route, although,, I may go back to tablet form if I can see that getting my vitamins balanced helps with my health issues.

I seem to be able to tolerate a small amount of lactose and was accounting for this in the tablet form but then there are other medication too that will affect this.

I never used to be lactose intolerant, however, post antibiotics and covid I am, but I hope it may be temporary.

I know you have mentioned dairy free and gluten free in previous posts, but I can’t manage this at the moment with my health the way it is and needing to rule out things before I trial this.

Thanks again.

[Sailing14 in reply to Sparklingsunshine]

Could I ask if I was to increase on the tablet I am on, would it help the absorption issues (if that is what I have) and therefore, I would receive more of the dose?

Also, did you try liquid for these reasons? I have just started liquid but I wake up with a headache, although, I feel I am receiving more of the hormone this way, but the hangover feeling is difficult.

Thank you

[Sparklingsunshine in reply to Sailing14]

No I've never been offered liquid. I'm currently on combi Levo/ T3 so have reduced Levo anyway. I would assume that if you increase your dose then theoretically it should improve the amount you absorb.

[Sailing14 in reply to Sparklingsunshine]

Thanks. That is useful to know as I did find I got on with the tablet I changed to recently. I will see how things go with the liquid and headache symptoms. Maybe it is the body getting used to a different form.

It is difficult to know at the moment if it is absorption issues or needing an increased dose (or both).

[jimh111]

It's just a rough first shot for people with no thyroid function.

[Sailing14 in reply to jimh111]

Thank you. That does make sense.