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To supplement or not to supplement Vitamin D? That is the question.
One of the many downsides of being hypothyroid, is the inability to absorb certain vitamins and minerals (often due to low stomach acid or poor gut health). Actually a hormone, Vitamin D is important for our joints, energy levels, immune system and also ties in to thyroid health too.
Low Vitamin D Levels and Hypothyroidism
Symptoms of Low or Deficient Vitamin D Include:
- Muscle and joint pain
- Muscle and joint weakness
- Bone ‘pain’
- Tiredness or fatigue
- Hair loss
Inadequate levels of Vitamin D can even stop your thyroid medication from working as well as it should do.
Many hypothyroidism patients have low or possibly even deficient Vitamin D levels and don’t realise it. You should therefore ask you doctor to test for 25-hydroxy D if you think you could have low levels. I didn’t suspect mine to be low but upon testing it was below range. Supplementing and getting my levels back up to optimal helped my health a lot.
The optimal level as reported by most sources for Vitamin D seems to be between 50-80ng/ml or as close to the top of the range as possible. I keep mine towards the top of this range with maintenance supplementation.
For those of us with Hashimoto’s as the cause for our hypothyroidism, it is also worth noting that Vitamin D has been shown to lower thyroid antibodies. 
Should You Supplement Vitamin D?
You will need to supplement Vitamin D if you’re low in it, and if you’re found to be deficient, you should receive this on prescription from a doctor. Usually a very high dose such as 50,000iu is given until levels return to within range.
Even if your levels are on the low side, but not deficient, it can still make you feel unwell, so it may be helpful to consider supplementation. However, it’s best to do this with a medical professional’s guidance.
It is also worth knowing that we should always take Vitamin D3 with Vitamin K2. This is because Vitamin D3 improves calcium absorption across the GI tract and Vitamin K2 is needed to transfer calcium into your bones and not your arteries.
Vitamin K2 regulates calcium in the blood, so combining Vitamin K2 with Vitamin D3 is often recommended because of the synergy between the two vitamins. Research shows a slower progression of calcification in those taking both vitamin K2 and vitamin D compared to those taking vitamin D alone. 
These are two really popular Vitamin D and Vitamin K supplements:
The NHS say to take no more than 25mcg a day , the US government say no more than 400iu a day, the Endocrine Society say 1,500–2,000iu a day and the Vitamin D Council say 5,000iu a day. So, it’s not completely clear!
It all depends on what you need. My functional medicine practitioner advised that I take 10,000ui until my levels came up (from 40 to 70) and then I reduced this to 4,000iu per day to maintain healthy levels and have done for years now. But it’s a good idea to regularly retest levels to check where they are.
You need to be cautious of taking too much, though, and The Vitamin D Council recommends taking no more than the upper limit of 10,000iu a day for adults. 
Signs of Too Much Vitamin D Include:
- Low appetite
- Excessive urination
- Weakness and nervousness.
You could make yourself feel worse by taking too much, so do test your levels before considering supplementing.
When To Take Vitamin D
If you do decide to supplement, then you should aim to take your Vitamin D3 supplement with dinner, as it’s the usually the fattiest meal of the day and helps with absorption.
Have you found that supplementing Vitamin D has helped?
You can click on the hyperlinks in the above post to learn more and see references to information given.
The online thyroid course ‘Freedom From Thyroid Fatigue‘, which walks you through how to overcome thyroid fatigue with a personalised approach.
Rachel Hill is the highly ranked and multi-award winning thyroid patient advocate, writer, speaker and author behind The Invisible Hypothyroidism. Her thyroid advocacy work includes writing articles, authoring books, producing her Thyroid Family email newsletters and speaking on podcasts, as well as being a founding board member for the American College of Thyroidology. She is well-recognised as a crucial contributor to the thyroid community and has a large social media presence. Her books include “Be Your Own Thyroid Advocate” and “You, Me and Hypothyroidism”.