Hashimoto’s Fatigue: Why You’re Still Tired and What to Ask

By Anna Curran, RN, BSN, PHN · Last reviewed October 2026

Hashimoto’s fatigue is the deep tiredness that often comes with an underactive thyroid. It usually improves once your thyroid hormone level is in a healthy range, but not always. If you are still tired on treatment, your dose may need adjusting, or something else, like anemia, low vitamin B12, poor sleep or depression, may be adding to it.

You are not imagining it. Here is why the tiredness can linger and what you and your doctor can check.

Why Hashimoto’s Fatigue Happens

Thyroid hormone helps set the pace for your whole body. When Hashimoto’s damages the thyroid and hormone levels drop, many systems slow down. Fatigue and feeling sluggish are among the most common symptoms of hypothyroidism.

Treatment with levothyroxine replaces the missing hormone. For many people, energy slowly returns over the following weeks to months as the dose is fine-tuned.

But for some, tiredness hangs on. In a Mayo Clinic chart review summarized by the American Thyroid Association, about 1 in 4 people treated with levothyroxine still reported symptoms even after their TSH was back in the normal range. Fatigue was the most common one.

The study did not find a single cause, so it helps to look at the whole picture.

Reason 1: Your Dose May Need Adjusting

The ATA lists ongoing tiredness, feeling cold and constipation as signs your dose may be too low. These are worth reporting.

Your dose can need changes when:

You recently started levothyroxine, and the dose is still being adjusted
You became pregnant
You started or stopped other medicines, such as estrogen or seizure medicines
Your pharmacy switched your brand or generic

Absorption matters too. Calcium, iron, some antacids and certain foods can block levothyroxine if you take them too close together. Our guide on how to take levothyroxine explains the timing.

Your doctor will usually check your TSH about 6 to 8 weeks after any dose change. The ATA notes that some people may also need a second medicine, liothyronine (T3), if they don’t feel better on T4 alone. That is a decision for you and your doctor.

Never change your dose on your own. Too much thyroid hormone can cause a racing heart, anxiety, trouble sleeping and bone loss.

Reason 2: Other Causes Your Doctor May Check

Mayo Clinic lists many conditions that can cause fatigue. Several are more likely, or worth a closer look, when you have Hashimoto’s.

Anemia

Anemia means you do not have enough healthy red blood cells to carry oxygen. Mayo Clinic notes it can make you feel worn out, weak or short of breath. It can also cause pale skin, dizziness and cold hands and feet.

Heavy periods are a common cause of low iron, according to Mayo Clinic. Heavy or irregular periods can also be a symptom of hypothyroidism, so this is worth mentioning.

Low vitamin B12

MedlinePlus lists Hashimoto’s as a condition that raises the risk of pernicious anemia, an autoimmune problem where the body cannot absorb vitamin B12 well. Low B12 can cause:

Fatigue and shortness of breath
Pale skin and a red, swollen tongue
Numbness or tingling in the hands and feet
Trouble with memory, focus or balance

Long-term low B12 can damage nerves, so testing is worth asking about.

Low vitamin D

Mayo Clinic includes low vitamin D among the causes of fatigue. A simple blood test can check your level. Ask your doctor before starting a supplement.

Sleep apnea

Obstructive sleep apnea causes repeated pauses in breathing during sleep. Mayo Clinic notes that hypothyroidism is one of the conditions linked to it.

Signs include loud snoring, waking up gasping or choking, morning headaches and feeling sleepy during the day, even after a full night in bed. Ask a bed partner if they have noticed pauses in your breathing. Sleep apnea is treatable, and treating it can make a real difference in energy.

Depression and anxiety

Low mood is a symptom of hypothyroidism, and depression and anxiety are both common causes of fatigue. Signs of depression include a low or empty mood most days, losing interest in things you enjoy, sleep changes and trouble concentrating.

These are medical conditions, not a weakness. Effective treatment is available, including talk therapy and medicine.

Other autoimmune conditions

Having one autoimmune disease raises the chance of another. Conditions linked with Hashimoto’s that can cause tiredness include:

Celiac disease, which can also affect how levothyroxine is absorbed
Type 1 diabetes
Addison’s disease, in which the adrenal glands do not make enough hormones
Rheumatoid arthritis, lupus and Sjögren’s syndrome

Your doctor will decide which tests make sense based on your symptoms.

Medicines and daily life

Mayo Clinic notes that some medicines can cause tiredness, including allergy and cough medicines, pain medicines, heart medicines and antidepressants. Alcohol, poor eating habits, too little sleep and too little (or too much) physical activity can play a part too.

Never stop a medicine on your own. Ask your doctor or pharmacist to review your list.

Sleep Tips for Better Energy

The CDC recommends that adults get at least 7 hours of sleep each night. A few habits can help you get the most from that time:

Keep a steady schedule. Go to bed and wake up at about the same time every day, even on weekends.
Make your room sleep-friendly. Cool, dark and quiet works best for most people.
Limit caffeine after lunch and go easy on alcohol in the evening.
Put screens away for a while before bed.
Wind down. Slow breathing, calming music or a warm shower can help signal that it is time to rest.

Pacing Your Energy

Pacing means spreading out your energy so you do not crash. It can help while you and your doctor sort out the cause.

Plan your hardest tasks for the time of day you feel best.
Break big jobs into small steps, with short rests in between.
Alternate heavier tasks with lighter ones.
Move a little each day. Short walks or light stretching can build energy over time. Ask your doctor before starting a new exercise routine, especially if your thyroid levels are not yet controlled.
Protect your limits. It is okay to say no or ask for help.

A simple two-week log of sleep, energy and symptoms can show patterns and give your doctor useful details.

Questions to Ask Your Doctor

Bring these questions to your next visit:

Is my TSH where it should be for me?
Could my dose need adjusting, or could something be affecting how I absorb my medicine?
Should I be checked for anemia, low iron or low vitamin B12?
Should we check my vitamin D level?
Could I have sleep apnea? Would a sleep study help?
Could depression or anxiety be part of this?
Should I be tested for other autoimmune conditions, like celiac disease?
Could any of my medicines or supplements be making me tired?

Bring a full list of everything you take, including vitamins and supplements. If you take biotin, tell your doctor, since it can affect thyroid test results.

When to Get Help

See your doctor if fatigue has not improved after two weeks of rest, healthy eating and enough fluids, as Mayo Clinic advises. Also call if your fatigue is getting worse or comes with new symptoms.

Call 911 or go to the ER if fatigue comes with:

Chest pain or shortness of breath
A fast or irregular heartbeat
Feeling like you might pass out
Severe belly, pelvic or back pain
Unusual bleeding
A severe headache

Get emergency care for extreme sleepiness or confusion, a very low body temperature or a very slow heartbeat, which can be signs of severe hypothyroidism. If you have thoughts of harming yourself, call or text 988 to reach the 988 Suicide & Crisis Lifeline.

Frequently Asked Questions

Why am I still tired if my TSH is normal?

A normal TSH means your thyroid levels look good, but other things can cause fatigue. Anemia, low B12, sleep apnea, depression and other conditions are common. Ask your doctor which tests make sense for you.

How long does it take for levothyroxine to help fatigue?

Cleveland Clinic says symptoms usually take a few weeks to improve, and finding the right dose can take a few tries. Your doctor will check your TSH about 6 to 8 weeks after each change.

Can Hashimoto’s fatigue come and go?

Yes. Energy can vary with sleep, stress, illness and other health changes. If tiredness returns after a good stretch, your dose may need checking.

Will a higher dose fix my fatigue?

Not always. If your levels are already in range, more thyroid hormone may cause side effects without helping. Your doctor will base your dose on your labs and symptoms.

The Bottom Line

Hashimoto’s fatigue often improves with the right dose of thyroid hormone, but it does not always go away completely. If you are still tired, your dose may need adjusting, or another cause like anemia, low B12, sleep apnea or depression may be involved. Good sleep habits and pacing can help in the meantime. Bring your questions to your doctor and ask for a full look at what might be draining your energy.