Can hypothyroidism or thyroid medication cause dizziness?

Qassi Gaba · 28 October 2026 · 5 min read

Short answer: dizziness is not one of the symptoms the NHS or NIDDK list for an underactive thyroid. That doesn't mean nothing in this area can cause it. A few things can, in both directions, too little hormone and too much, and they're worth knowing apart from each other.

If that's enough, you can stop here.

What the standard symptom lists actually say

The symptoms most consistently attached to hypothyroidism, across the NHS, NIDDK, and the American Thyroid Association, are tiredness, weight gain, feeling cold, dry skin, hair thinning, constipation, low mood, and muscle aches. Dizziness isn't on any of these lists. NICE's clinical summary for UK clinicians describes it the same way: a slow-building set of nonspecific symptoms, with dizziness not among the named ones.

That gap matters, because dizziness is extremely common on its own. Most people who feel dizzy at some point don't have a thyroid problem, and most people with a thyroid problem don't list dizziness as their main complaint. When the two show up together, it's often coincidence, or something adjacent to the thyroid rather than the thyroid itself.

Where it can genuinely connect

A few mechanisms are documented, even if dizziness itself isn't the headline symptom.

Hypothyroidism can run alongside anemia. Untreated or undertreated low thyroid function slows a lot of metabolic processes, and NIDDK's overview notes it as a condition that can coexist with other issues affecting energy and circulation. Anemia from any cause can produce lightheadedness, particularly on standing.

Hashimoto's thyroiditis, the autoimmune condition behind most hypothyroidism in iodine-sufficient countries, is itself an autoimmune disease, and the ATA's page on it notes that people with one autoimmune condition are more likely to have another. Some autoimmune conditions that can run alongside it affect vitamin B12 absorption or blood pressure regulation, either of which can produce dizziness on its own, separate from the thyroid itself.

Severe, longstanding hypothyroidism can also affect heart rate and blood pressure, both of which matter for how dizzy a person feels, particularly on standing up. None of this makes dizziness a thyroid symptom in the way tiredness or cold intolerance are. It makes it a symptom that sits near enough to the thyroid's effects that it's reasonable to mention to a doctor rather than dismiss.

Does levothyroxine itself cause dizziness

Levothyroxine, sold under various brand names including Synthroid, is a synthetic version of the hormone the thyroid normally makes. At the right dose it's replacing something the body is short of, not adding something foreign, so the drug itself isn't generally associated with dizziness as a direct effect.

What can cause it is the dose being higher than what the body needs. The drug's own US labeling lists the adverse effects of overtreatment as the same cluster seen in an overactive thyroid: palpitations, rapid heartbeat, tremor, sweating, anxiety, and insomnia. The NHS page on an overactive thyroid lists a fast or irregular heartbeat among the common symptoms, and a heart racing or skipping is one of the more common things people describe as dizziness even when it isn't, strictly, a balance problem.

The ATA's guidance on thyroid hormone treatment describes overtreatment in terms of this same symptom pattern and the importance of checking dose against TSH over time rather than guessing. It doesn't name dizziness either, but a racing heart and dizziness often arrive together, and overtreatment is one of the more plausible explanations when someone on levothyroxine develops dizziness that wasn't there before.

Undertreatment, hormone levels still too low, works the other way: it brings back the broader hypothyroid picture, tiredness and cold intolerance and the rest, with the same loose, indirect relationship to dizziness described above.

Why it's so hard to pin down from the symptom alone

Dizziness is a word that covers several different sensations. Lightheadedness on standing, a spinning sensation, unsteadiness on your feet, and a vague fogginess are all called "dizzy" by the people describing them, and they point toward different causes. Blood pressure, inner ear problems, medication side effects, anemia, blood sugar, anxiety, and dehydration are all far more common explanations than thyroid status, with or without a thyroid condition in the picture.

This is also why reading one lab result against one symptom tends to mislead. TSH and Free T4 move for a lot of reasons unrelated to how someone feels on a given day, and a single value next to a single symptom rarely tells a doctor much on its own. What tends to help is a pattern: when the dizziness started, whether it tracks with a dose change, what else was different that week, whether it happens on standing or at rest.

What's worth bringing to an appointment

Writing down when the dizziness happens, whether it's worse on standing, whether it followed a change in dose, and what else changed around the same time, gives a doctor something to work with that "I feel dizzy sometimes" doesn't. If it's new since starting or changing levothyroxine, saying so plainly is useful, since overtreatment is one of the more checkable explanations and a dose adjustment is something only a prescriber can assess properly.

Whether any of this applies to a particular case, and what it means for a particular dose, is a question for whoever is managing the treatment, not something a symptom list online can answer.

Where this fits with Haloscan

The app doesn't diagnose dizziness or tell anyone whether their dose is the cause of it. What it does is keep dose changes, symptoms, and lab dates on the same timeline, so if dizziness shows up after a dose change, that's visible as a pattern in the two-page report rather than something you have to reconstruct from memory in the waiting room.