Red Light Therapy for Thyroid Health: Shining a Light on the Science

We aren't making any claims in this article; We are simply sharing research.

Red light therapy is emerging as a fascinating area of research for thyroid health. Discover how it may support energy levels and help manage symptoms associated with both hypothyroidism and hyperthyroidism.

Hypothyroidism, often described as a “slow thyroid,” is far from an abstract diagnosis. It can noticeably drain energy, promote weight gain, disrupt other hormones, cloud thinking, and leave the body feeling unusually cold.

In many ways, the thyroid acts like a central dial for energy regulation. When it turns down, the entire system feels it. The biology is far more complex than a single switch, of course, but the metaphor holds.

Here’s the encouraging part.

Red light therapy has built a strong and growing research record in the context of hypothyroidism. The evidence is less developed for hyperthyroidism, where the thyroid is overactive, but that area is still under investigation. As with most endocrine topics, the thyroid’s interactions with the rest of the body are intricate, and the science continues to evolve.

This article reviews the available human research on red light therapy and hypothyroidism. The goal is to clarify what the science suggests about its potential role in supporting thyroid function, energy levels, temperature regulation, and common skin-related concerns associated with an underactive thyroid.

Introduction: Why Thyroid Health Matters More Than You Think

The thyroid plays a foundational role in overall health. While public awareness of thyroid function has improved compared to a decade ago, there is still much to learn and understand.

Few figures have influenced modern discussions on thyroid health as strongly as the late health researcher Ray Peat. Through extensive writing, Peat emphasized the central importance of thyroid function and argued that hypothyroidism, often described as a “slow” thyroid, is far more widespread in modern society than commonly recognized (1; 2; 3).

The sections that follow take a closer look at these ideas and how they relate to current thinking on thyroid health.

Thyroid Function: The Engine Behind Energy Metabolism

The thyroid functions much like the ignition for metabolism. When it operates well, the body burns energy more efficiently and overall health tends to follow. A core idea emphasized by Peat is that stronger thyroid function allows the body to produce more usable energy.

Energy underpins every biological process. Without it, life would cease almost immediately, as mitochondria would no longer generate the electrochemical energy required to sustain cells (4). Higher energy availability generally aligns with better resilience and health, while chronically low energy reflects a system under strain.

The thyroid sits at the heart of the body’s energy-producing systems. When energy production is sufficient, many disease processes are less likely to take hold. This concept overlaps closely with mitochondrial health, since mitochondria are the cellular structures responsible for generating energy and play a central role in preventing most modern, non-genetic diseases.

That said, thyroid health is highly complex. It is shaped by a wide range of interacting factors, far too many to list comprehensively. Some of these will be revisited shortly, but one stands out as especially influential: adequate energy intake, with carbohydrates in particular playing a key role.

Some individuals do thrive on low-carbohydrate or carnivore-style diets, but these approaches are not universally effective. From an evolutionary perspective, early human diets, particularly in equatorial regions, were typically rich in carbohydrates sourced from fruits, honey, tubers, and similar foods (5). For survival, hunter-gatherer populations would not have deliberately excluded carbohydrate-rich foods.

This perspective aligns closely with Peat’s views, which emphasize carbohydrates as a preferred fuel for overall metabolic and thyroid health (6). In contrast, prolonged ketosis or strict carbohydrate avoidance, especially when combined with limited protein intake, has been associated with metabolic states resembling starvation and may not support optimal human physiology over the short to mid term (7).

Next, it’s helpful to understand how thyroid function can be properly assessed. This area relies heavily on laboratory testing, and despite its importance, it remains widely misunderstood by many people:

Understanding Thyroid Testing

One of Peat’s core arguments is that standard thyroid lab panels are often inadequate (8; 9). Until fairly recently, many labs focused almost exclusively on measuring TSH, a practice that still creates confusion today.

TSH, or thyroid-stimulating hormone, reflects how much signal the pituitary gland is sending to the thyroid. Its role is indirect: TSH tells the thyroid to produce the hormones T4 and T3. Of these, T4 is largely inactive and must be converted into T3, the biologically active hormone that actually drives metabolic effects in the body.

Because of this, a normal TSH result or treatment with T4 alone does not necessarily confirm that the thyroid system is functioning optimally. Without assessing downstream hormone activity, it’s impossible to know whether thyroid signaling, conversion, and tissue-level effects are truly aligned.

And the reason why is that it doesn’t show whether the body has adequate T3 or whether that T3 is functioning properly at the tissue level.

Jay Feldman, widely regarded as one of the leading authorities on Ray Peat’s work today, describes this dynamic as follows:

"So, when T3 and T4 are low, as in the low-energy state, or “low-battery mode,” TSH is generally higher. The opposite is generally true in the high-energy state, or “high-performance mode.”

TSH levels seemed like a good indicator of hypothyroidism based on the above process. So, once it could be easily measured with a blood test, it became the standard diagnostic measure for hypothyroidism. In the meantime, the other symptoms and diagnostic tests became more or less forgotten.

However, TSH is a much less direct measure of thyroid and metabolic status, so it is not as well correlated with thyroid function. For example, infections, caffeine, and chronic stress can all lower TSH, even if the thyroid hormones are low. In other words, your TSH can be within the “normal range,” and you can still be in a hypothyroid state." (9).

In this context, hypothyroidism doesn’t simply mean a “slow” thyroid, but rather a thyroid system that isn’t functioning efficiently and disrupts metabolic processes.