Hypothyroidism and feeling cold: a deeper guide
Hypothyroidism makes you feel cold because low thyroid hormone slows the body's metabolism, so it produces less heat at rest and less extra heat when you are chilled. In a Swiss study, restoring normal thyroid levels raised the body's heat response to mild cold by about 102%. Most people warm up with proper treatment, but persistent cold deserves a talk with your clinician.
Why does hypothyroidism make you feel cold?
Thyroid hormone sets the pace of the body's metabolism. Cleveland Clinic describes hypothyroidism as a condition that slows your metabolism, and every metabolic process gives off heat as a by-product. Less hormone means a smaller internal furnace.
The effect is measurable. In a 2019 study in the journal Thyroid, researchers in Basel measured energy use in 33 adults with hypothyroidism before and after at least three months of hormone replacement. Resting energy use in warm conditions rose from 1,330 to 1,442 kcal per day, an 8.5% increase.
The bigger change came in the cold. Cold-induced thermogenesis, the extra heat the body makes during a mild chill, rose from a median of 55 to 111 kcal per day once thyroid levels were normal. In other words, an underactive thyroid blunts both your baseline heat and your ability to respond when the room or the weather turns cold.
What does hypothyroid cold intolerance feel like?
MedlinePlus, from the National Library of Medicine, gives a plain picture: wearing a sweater when others are wearing a t-shirt. It is listed among the early symptoms, alongside fatigue, constipation, dry skin, weakness and weight gain.
NIDDK notes that symptoms often develop slowly and may go unnoticed for months or years, so many people simply adjust the thermostat or add a layer. Left untreated, later signs can include a puffy face, slow speech, a slow heart rate and a low body temperature.
Cleveland Clinic also lists numbness or tingling in the hands. That matters for warmth: skin with reduced feeling is easier to burn with a heating pad or warmer, because you may not notice when it is too hot.
Can hypothyroidism and anemia both cause cold intolerance?
Yes, and they can occur together, which is why the search "cold intolerance causes anemia hypothyroidism" is so common. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) lists pernicious anemia, celiac disease, type 1 diabetes, rheumatoid arthritis and lupus among conditions that raise the risk of hypothyroidism.
Neither symptom points to one cause, so the answer comes from testing rather than guessing. Our general guide to cold intolerance covers anemia and other causes in more depth.
| Question | What sources say |
|---|---|
| Which blood tests check the thyroid? | TSH and free T4 are the two main tests; TSH rises when the thyroid underproduces (American Thyroid Association) |
| How common is hypothyroidism? | Nearly 5 in 100 Americans aged 12 and older; most cases are mild (NIDDK) |
| Who is at higher risk? | Women, people over 60, people with a family history, and people pregnant in the past 6 months (NIDDK) |
| Can symptoms alone confirm it? | No; a history, exam and blood tests are needed (NIDDK) |
Why am I still cold on levothyroxine?
Levothyroxine starts adjusting hormone levels right away, but Cleveland Clinic says symptom improvement usually takes a few weeks. NIDDK and the American Thyroid Association (ATA) both describe a blood test 6 to 8 weeks after starting or changing a dose, so the first weeks are often a period of fine tuning.
The ATA lists feeling tired, cold or constipated as possible signs of too little medicine. Absorption matters too: calcium and iron supplements, antacids, biotin, estrogen and some seizure medicines can affect thyroid pills, and MedlinePlus advises taking some supplements and medicines at least 4 hours apart from thyroid medicine. Tell your prescriber about anything you start or stop.
Some people still feel unwell with normal labs. In a Mayo Clinic chart review summarized by the ATA, about 27% to 28% of treated patients had new or ongoing hypothyroid symptoms despite a normal TSH at follow-up, most often fatigue and weight gain. The cause was not identified, and other conditions may have played a part.
The ATA notes that some people who do not feel better on T4 alone are given liothyronine (T3). Decisions about dose or type of medicine belong to you and your prescriber; never change or stop thyroid medicine on your own.
How can you stay warmer while your levels settle?
Practical warmth works best when it keeps the heat your body already makes. Because hypothyroidism lowers heat production, insulation does more for you than brief bursts of added heat.
Layer a snug base layer, an insulating middle layer and a wind-blocking shell outdoors.
Keep your torso and neck warm; a warm core makes it easier for blood to keep flowing to the hands and feet.
Wear socks and slippers indoors, since cold floors pull heat from the feet.
If your hands or feet feel numb or tingly, keep heating pads and warmers off bare skin, use timers, and check your skin afterward.
Keep a log of when you feel cold and share it at your next appointment; it helps your clinician judge whether the dose is right.
When to call a clinician or emergency services
Myxedema coma is a rare, life-threatening complication of severe untreated hypothyroidism. MedlinePlus notes it can be triggered by infection, illness, cold exposure, certain medicines or not taking thyroid medicine consistently.
Call 911 for very low body temperature with extreme drowsiness, slow or difficult breathing, a slow heartbeat, low blood pressure, confusion or unresponsiveness.
Call your clinician promptly for chest pain or a rapid heartbeat while on treatment, symptoms that worsen or do not improve, or new symptoms.
Book a visit if you are newly and persistently colder than people around you, especially with fatigue, dry skin or weight gain.
Key takeaways
Low thyroid hormone reduces both resting heat production and the extra heat the body makes in the cold.
Restoring normal thyroid levels roughly doubled cold-induced heat production in a 2019 study.
Feeling cold on levothyroxine can reflect early dose adjustment, absorption problems or another cause; testing guides the answer.
Hypothyroidism and anemia can occur together, so persistent cold intolerance deserves blood tests rather than guesswork.
Very low body temperature with drowsiness or slow breathing is an emergency.
Frequently asked questions
Does hypothyroidism make your hands and feet cold?
It can. Low thyroid hormone reduces overall heat production, and many people notice it first in their hands and feet. Cleveland Clinic also lists numbness or tingling in the hands, so take care with heat sources on skin that feels less.
How long after starting levothyroxine will I stop feeling cold?
Cleveland Clinic says symptom improvement usually takes a few weeks. Blood levels are typically rechecked 6 to 8 weeks after starting or changing a dose, so it can take a few rounds of adjustment. Talk to your prescriber if you remain cold.
Can subclinical hypothyroidism make you feel cold?
Possibly. The 2019 Basel study included people with subclinical or overt hypothyroidism and found that cold-induced heat production rose after treatment. Cleveland Clinic notes that mild subclinical hypothyroidism often resolves on its own within about three months, so your clinician may recheck before deciding on treatment.
Can taking too much thyroid medicine make you feel hot?
Yes. The American Thyroid Association lists feeling hot, a fast heartbeat, nervousness and weight loss as possible signs of too much medicine. Report these to your prescriber rather than adjusting the dose yourself.
Should I get tested for anemia and thyroid problems if I am always cold?
If cold intolerance is new, persistent or comes with fatigue, both are reasonable things to ask your clinician about. Symptoms alone cannot tell them apart, and the two conditions can occur together.
From HEATJAC
We design low-profile thermal garments: a heat-reflective vest and a thermal harness with pockets for warmers or cold packs. If you have reduced sensation or a health condition, check with your clinician before adding heat.
Choosing gear? Before you buy: a checklist for any warming garment · What actually helps someone who is always cold
Related reading
Sources
Hypothyroidism (Underactive Thyroid), National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Hypothyroidism, MedlinePlus, National Library of Medicine
Hypothyroidism (Underactive Thyroid), American Thyroid Association
Hypothyroidism (Underactive Thyroid), Cleveland Clinic
Why do so many patients receiving levothyroxine treatment for hypothyroidism have persistent symptoms?, American Thyroid Association, Clinical Thyroidology for the Public
About HEATJAC. HEATJAC is a thermal architecture company founded by an anesthesiologist. We design patented garment systems that capture, conduct and broaden warmth across the body, and we publish this knowledge hub because the science of staying warm should be public. HEATJAC products are not medical devices and are not intended to diagnose, treat, cure or prevent any disease.