Thyroid UK
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How to gain weight when hypothyroid? (TTC)

I have been recently started on levothyroxine having been incidentally diagnosed with hypothyroidism (tsh 6.4 ( 0.5-4) and t4 8.7 (9.6-25) my thyroid antibodies are only top end of normal 32 (0-34) although in hindsight apart from no weight gain I was showing quite a few symptoms (I have a BMI of only 18.7) . I also have pcos again diagnosed recently during routine fertility checks prior to starting reciprocal ivf (incidentally I have recently come off the pill having been on the pill for 9 years but due to very irregular cycles for 6 months have gone back on the pill based on consultants advice until starting ivf )

I need to increase my BMI before starting reciprocal ivf treatment (as well as sorting out thyroid) but since starting levothyroxine the weight I had gained I am loosing. What would be the best foods to eat to gain weight but also not make pcos or hypothyroidism worse? I don't have a huge appetite though. People say just eat more but this is so much easier said than done and just eating extra junk food doesn't work ( I would say I have a relatively balanced diet ATM but have tried to have a dessert at least once a day with 400 extra calories. )

Thanks for any advice or experience from people in similar situations

2 Replies


I was advised to eat frequent small meals in order to gain weight. I also found protein shakes helpful in between meals. The only food you need to avoid is unfermented soy but junk food doesn't sound like a good diet option.

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.

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.

You should have a follow up thyroid test 6-8 weeks after starting Levothyroxine. Arrange an early morning and fasting (water only) blood draw when TSH is highest, and take Levothyroxine after your blood draw.


When my dad had cancer and needed to increase his weight, the nutritionist advised things like swapping skimmed milk to full fat, adding cream to cooking, using butter instead of low fat spread, that kind of thing. That has the effect of adding calories without making you actually have to eat more food.


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