Vitamin D and the thyroid are two small things that do big jobs inside the body.
When either one stops working well, the whole body can feel tired, slow, and sore.
Many people with low thyroid, also called hypothyroidism, also have low vitamin D.
Doctors around the world have noticed this pattern again and again.
This article explains everything in very easy words.
No big medical talk.
No confusion.
Just clear ideas, one step at a time.
What Is the Thyroid?
The thyroid is a small gland in the neck.
It looks like a tiny butterfly.
The thyroid acts like a speed button for the body.
It helps control:
- How fast the heart beats
- How warm the body feels
- How much energy the body has
- How the brain thinks
- How bones grow
- How hair grows
When the thyroid works well, the body feels balanced.
What Is Low Thyroid?
Low thyroid means the thyroid is too slow.
Doctors call this hypothyroidism.
When the thyroid is slow, the body slows down too.
A person with low thyroid may feel:
- Very tired
- Cold even in warm weather
- Sad or low
- Forgetful
- Weak
- Heavy or puffy
- Sore in muscles and joints
Low thyroid can happen to adults, children, and even babies.
What Is Vitamin D?
Vitamin D is a helper vitamin.
It acts like a sunshine helper inside the body.
Vitamin D helps the body:
- Build strong bones
- Keep teeth strong
- Control calcium
- Support the immune system
- Keep muscles working
- Lower swelling inside the body
The body makes vitamin D when skin touches sunlight.
That is why people call it the sun vitamin.
Where Does Vitamin D Come From?
Vitamin D comes from three main places.
Sunlight
When sunlight touches the skin, the body makes vitamin D.
Short sun time helps, but many people do not get enough sun.
Dark skin, old age, and staying indoors reduce vitamin D production.
Food
Only a few foods have vitamin D.
These foods include:
- Fish like sardines and mackerel
- Egg yolks
- Cheese
- Beef liver
The amount from food is small.
Supplements
Many people need vitamin D tablets or drops.
Doctors often suggest them when blood levels are low.
What Is Vitamin D Deficiency?
Vitamin D deficiency means the body has too little vitamin D.
Doctors measure vitamin D with a blood test called 25-OH vitamin D.
A level below 20 ng/ml means deficiency.
Many adults and children around the world have low vitamin D and do not know it.
Signs of Low Vitamin D
Low vitamin D does not always shout.
Sometimes it whispers.
Common signs include:
- Tiredness
- Body pain
- Weak muscles
- Bone pain
- Getting sick often
- Low mood
In children, low vitamin D can cause:
- Soft bones
- Bent legs
- Slow growth
- Late walking
In adults, it can cause:
- Bone weakness
- Bone pain
- Trouble standing or climbing stairs
How Vitamin D and Low Thyroid Connect
Doctors and researchers noticed something important.
Many people with low thyroid also have low vitamin D.
This link appears often in blood tests and studies.
Vitamin D helps the immune system stay calm.
The immune system protects the body from harm.
Low thyroid often comes from autoimmune disease, where the immune system attacks the thyroid by mistake.
Vitamin D may help reduce this attack.
What Research Shows
A study compared two groups of people.
- 30 people had hypothyroidism
- 30 people were healthy
Doctors checked:
- Vitamin D levels
- Thyroid hormones
- Calcium levels
What They Found
- People with low thyroid had much lower vitamin D
- Calcium levels were also lower
- The worse the thyroid problem, the lower the vitamin D
Women had slightly lower vitamin D than men, but the difference was small.
Why Calcium Matters
Calcium helps build bones and teeth.
Vitamin D helps the body use calcium.
When vitamin D is low:
- Calcium drops
- Bones weaken
- Muscle pain starts
People with hypothyroidism often have low calcium too.
This explains why many feel bone pain and muscle weakness.
Why Doctors Suggest Vitamin D for Low Thyroid
Doctors now suggest:
- Testing vitamin D in people with low thyroid
- Checking calcium levels
- Using vitamin D supplements when needed
Vitamin D does not cure thyroid disease, but it may support the body.
It may help:
- Bone strength
- Muscle strength
- Immune balance
- Overall comfort
Is Vitamin D a Cure for Thyroid Disease?
No.
Vitamin D does not replace thyroid medicine.
Thyroid hormone pills still matter.
Vitamin D acts as a helper, not a replacement.
If you want to learn more about treatment options, read this detailed guide on how to cure thyroid safely and correctly.
Vitamin D and Autoimmune Thyroid Disease
Autoimmune thyroid disease includes:
- Hashimoto’s thyroiditis
- Graves’ disease
Vitamin D helps calm immune reactions.
Some research suggests vitamin D may reduce immune attack on the thyroid.
This does not mean it stops disease, but it may reduce stress on the gland.
You can also read how vitamin D links with fast thyroid in this article on vitamin D and hyperthyroidism.
Vitamin D and Pregnancy With Thyroid Problems
Pregnancy changes hormone needs.
Low vitamin D during pregnancy links with:
- Blood sugar problems
- Bone issues
- Higher health risks
Women with thyroid disease should check vitamin D early.
This guide explains how to control thyroid during pregnancy step by step.
How Doctors Test Vitamin D
Doctors use a blood test called 25-hydroxyvitamin D.
They may also test:
- Calcium
- Phosphate
- Thyroid hormones
Testing helps guide the right dose.
How Vitamin D Deficiency Is Treated
Treatment depends on how low the level is.
Mild Low Levels
- Short sun exposure
- Low-dose supplements
Severe Low Levels
- Higher-dose tablets
- Liquid vitamin D
- Sometimes injections
Doctors often give a strong dose first, then a daily small dose.
Which Vitamin D Is Best?
There are two main types:
- Vitamin D2
- Vitamin D3
Vitamin D3 works better for most people.
It matches what the skin makes from sunlight.
Can Vitamin D Cause Side Effects?
Vitamin D is safe in normal doses.
Very high doses can raise calcium too much.
Signs include:
- Thirst
- Nausea
- Headache
- Frequent urination
Always follow doctor advice.
Medicines That May Affect Vitamin D
Some drugs reduce vitamin D levels.
Examples include:
- Steroids
- Some seizure medicines
- Some mood medicines
Tell your doctor about all medicines you use.
Vitamin D, Hair, and Thyroid
Low thyroid often causes hair loss.
Low vitamin D may make it worse.
Healthy vitamin D levels support hair growth.
You may also like this expert review of the best shampoo for thyroid hair problems.
Bone Pain, Veins, and Weakness
Low vitamin D affects blood flow and muscle tone.
Some people with thyroid disease also report leg pain and vein issues.
This in-depth guide on varicose veins relief creams explains helpful options.
Simple Daily Tips for Vitamin D
Here are easy habits:
- Sit in sunlight for short periods
- Eat eggs and fish when possible
- Take supplements if advised
- Test levels once or twice a year
Small steps help over time.
Prognosis
Most people improve after vitamin D treatment.
Pain reduces slowly.
Energy improves gradually.
Bones get stronger.
Severe bone damage may not fully reverse, but early treatment helps a lot.
When to Talk to a Doctor
Speak to a doctor if you have:
- Long-term tiredness
- Bone pain
- Muscle weakness
- Thyroid disease history
- Pregnancy plans
Testing helps find answers early.
Thyroid and Vitamin D: Frequently Asked Questions
Understanding the relationship between vitamins and thyroid health is essential for effective management. Here are some of the most common questions regarding Vitamin D and thyroid function.
1. Can I take Vitamin D with thyroid medication?
Yes, you can generally take Vitamin D while on thyroid medication. In fact, many people with thyroid disorders are also deficient in Vitamin D. However, it is always best to consult your doctor to ensure the dosage is correct for your specific needs. For more detailed information on how these interact, especially in cases of overactive thyroid, read about Vitamin D and hyperthyroidism.
2. Can too much Vitamin D cause thyroid problems?
While Vitamin D is essential, excessive amounts (toxicity) can lead to complications like hypercalcemia, which may mimic or exacerbate certain thyroid-related symptoms. Maintaining a balance is key. If you are looking for ways to manage your condition naturally or through lifestyle changes, explore how to cure thyroid issues effectively.
3. Can I take Vitamin D and levothyroxine together?
Yes, but timing is important. Levothyroxine should ideally be taken on an empty stomach, at least 30-60 minutes before breakfast. While Vitamin D doesn’t typically interfere with the absorption of levothyroxine, some calcium-enriched Vitamin D supplements might. If you are managing thyroid health during a sensitive time, such as expecting a child, see our guide on how to control thyroid during pregnancy.
4. Can you take Vitamin D if you have an underactive thyroid?
Absolutely. Research suggests that Vitamin D supplementation may help improve TSH levels in people with hypothyroidism (underactive thyroid). Supplementing can also help with secondary symptoms like thinning hair. If you are experiencing hair loss due to your condition, you might also want to look into the best shampoo for thyroid hair.
5. What vitamin is good for a low thyroid?
Besides Vitamin D, vitamins such as B12, Selenium, and Zinc are vital for patients with low thyroid function. Proper supplementation can help boost energy and improve circulation. If you suffer from related circulatory issues like heavy or aching legs, you can check out our varicose veins relief cream reviews for topical support.
Final Thoughts
Vitamin D is small, but powerful.
Low thyroid and low vitamin D often walk together.
Testing, supplements, and care support better health.
Vitamin D does not replace thyroid medicine, but it supports the body in quiet ways.
Think of vitamin D as a helper friend for the thyroid.
Reference
The following resources provide detailed scientific insights and clinical guidance regarding Vitamin D, its deficiency symptoms, and its critical link to thyroid health.
- Vitamin D – Factsheet for health professionals – National Institutes of Health.
- All you need to know about fat-soluble vitamins – Medical News Today.
- What Have We Learned About Vitamin D Dosing? – Joseph Pizzorno, ND.
- Hypovitaminosis D in British adults at age 45 y: a nationwide cohort study – Hyppönen E, Power C. (Am J Clin Nutr).
- Distribution analysis of vitamin D highlights differences in population subgroups – Pal BR, et al. (J Endocrinol).
- Vitamin D deficiency: Musculoskeletal disorders – Dr. Louise R. Newson.
- Vitamin D Deficiency in Adults: When to Test and How to Treat – Kennel KA, Drake MT, Hurley DL.
- NHS Guidance: Vitamin D – Official NHS resource.
- Vitamin D deficiency in children – NHS Nottingham University Hospitals.
- Vitamin D status during pregnancy and the risk of gestational diabetes mellitus – Xia J, et al.
- Vitamin D Lab Test Information – MedlinePlus.
- Vitamin D Deficiency including Osteomalacia and Rickets – Patient.info.
- NICE Guidelines: Vitamin D deficiency in adults – treatment and prevention – NICE.
- Vitamin D in Children Clinical Services – RNOH.
- Health claims about vitamin D examined – Nursing Times / NHS News Analysis.
- Vitamin D: Drugs and Supplements – Mayo Clinic.
- Vitamin D Intake and the Risk of Incident Kidney Stones – Ferraro PM, et al. (The Journal of Urology).
- Drug-vitamin D interactions: a systematic review – Robien K, et al. (Nutr Clin Pract).
- What is vitamin D toxicity? – Mayo Clinic Expert Answers.
- The Role of Vitamin D Deficiency in Thyroid Disorders – Chris Kresser.
- Vitamin D Deficiency and its Association with Thyroid Disease – Mackawy AM, Alayed BM, Al-rashidi BM. (Int J Health Sci).
- Everything you need to know about rickets – Medical News Today.
- The Importance of Vitamins and Minerals in Hypothyroidism – Thyroid UK.
- Recent advances in Vitamin D Research (2025) – Frontiers in Nutrition.
- Thyroid Hormone and Vitamin D Signaling – Taylor & Francis Online.
- Vitamin D and Autoimmune Diseases – International Journal of Molecular Sciences.
- Clinical Review of Vitamin D Status – European Journal of Medical and Health Research.