Cold Intolerance

Always feeling cold is a signal from metabolism, circulation, or the nervous system. We look at the brain thermostat, thyroid conversion, iron, mitochondria, fuel, and autonomic regulation.

What you may be noticing

Everyone else is comfortable, and you reach for a sweater. Your hands and feet stay cold, even in bed. Air conditioning feels punishing. You may also notice fatigue, dry skin, constipation, or brain fog.

Why it is rarely one thing

Body temperature is governed by the brain. The hypothalamus sets the target, directs thyroid output through TRH and TSH, and controls blood flow to the skin through the sympathetic nervous system. Heat production comes largely from metabolism in muscle, liver, and brown fat, driven by active thyroid hormone and mitochondria.

Feeling cold can come from either side. Low free T3, high reverse T3, iron deficiency, anemia, low muscle mass, under-eating, and low body fat reduce heat production. Sympathetic overdrive, Raynaud phenomenon, and dysautonomia restrict blood flow to the hands and feet. Not simply a cold person, but a system conserving heat for a reason.

In my clinical experience, cold intolerance often travels with a body in conservation mode: chronic stress, inflammation, or a heavy toxic burden that slows thyroid conversion and mitochondrial output. This is a working hypothesis that guides where I look first. Cold all over points toward metabolism and fuel. Cold hands and feet with a warm core points toward circulation and the autonomic nervous system.

Patterns we look for

• TSH, free T4, free T3, and reverse T3, read as a pattern.
• Iron, ferritin, and hemoglobin.
• B12 and folate.
• Calorie intake, chronic dieting, and low body fat.
• Muscle mass and activity level.
• Blood sugar regulation.
• Autonomic balance and Raynaud patterns.
• Mitochondrial function.
• Inflammatory and toxic burden.
• Adrenal and pituitary function when other signs suggest them.

How I evaluate it

The comprehensive functional neurological exam assesses autonomic responses, including skin temperature and color changes, capillary refill, heart rate variability, and blood pressure on standing. Reflex timing and cognitive speed offer additional clues about thyroid activity in the nervous system.

Functional labs may include a full thyroid panel with reverse T3 and antibodies, a complete blood count, ferritin and iron studies, B12, fasting glucose and insulin, a comprehensive metabolic panel, and a cortisol rhythm. An organic acids test can add insight into mitochondrial energy metabolism. Persistent abnormal findings lead to endocrine referral.

A temperature and symptom log, noting time of day, meals, and stress, often clarifies the pattern.

How we address it

• Identify whether the main driver is heat production, heat loss, or both.
• Calm sympathetic overdrive first, so circulation and conversion can respond.
• Rebalance thyroid conversion where indicated.
• Replete iron, B12, selenium, and other nutrients.
• Eat enough, with adequate protein and regular meals.
• Build muscle with strength training and support mitochondria with nutrient categories that serve cellular energy.
• Open drainage pathways before addressing deeper toxic burden.
• Restore circulation with autonomic training, movement, and gentle contrast temperature practices where appropriate.

Warmth is a sign of a body that feels resourced and safe. Many people notice it returning first to the core, then to the hands and feet.

Book your Comprehensive Functional Medicine Eval/Neurological Exam today to discover what the contributing root causes are that are underlying your health concerns.