Feeling cold all the time: causes, red flags and when to get it checked

Body temperature is regulated by metabolism, muscle mass, blood flow and the thyroid and adrenal hormones. If heat production is low, or blood is diverted from the skin, you feel cold. A persistent change from your usual tolerance suggests a medical contributor worth checking.

• Normal variation: smaller body size, low body fat, age and being female.

• Underactive thyroid (hypothyroidism), commonly autoimmune (Hashimoto thyroiditis), more common in women and with age.

• Iron deficiency and other anaemias, from heavy periods, diet or bowel disease.

• Low body weight, eating disorders and undereating.

• Raynaud phenomenon and poor circulation affecting hands and feet.

• Vitamin B12 deficiency, diabetes and kidney disease.

• Low blood pressure, adrenal insufficiency and pituitary disorders.

• Medicines such as beta blockers, and infections or cancers causing weight loss; hypothermia in older adults and those with alcohol use.

Marked tiredness, rapid weight gain or loss, slow pulse, confusion, severe constipation, swelling of face, hoarse voice, fainting, low blood pressure, salt craving, darkening skin, or coldness with drowsiness in an older person need prompt assessment.

• Call 999: confusion or drowsiness with cold skin and shivering stopping (possible hypothermia), or collapse.

• Same-day GP: coldness with severe weakness, fainting, vomiting or abdominal pain.

• GP within weeks: persistent cold intolerance with fatigue, weight gain or hair and skin changes.

• Routine: lifelong cold sensitivity without other symptoms.

The doctor asks when it began, tiredness, weight changes, appetite, periods, bowel habit, mood, skin and hair changes, diet, medicines and family history of thyroid disease. They examine pulse, blood pressure, skin, thyroid, reflexes and for pallor and swelling.

• Thyroid function (TSH and free T4): the key test for underactive thyroid.

• Full blood count and ferritin: for anaemia and iron deficiency.

• Vitamin B12 and folate, glucose or HbA1c, kidney function.

• Morning cortisol: if adrenal insufficiency is suspected.

• Thyroid antibodies if autoimmune thyroid disease is suspected.

Dress in warm layers, keep rooms comfortably heated, eat regular meals with enough protein and calories, stay active and avoid alcohol excess. Do not use unproven thyroid supplements. If thyroid hormone is prescribed, take it exactly as directed and have levels monitored.

The NHS route is a GP and blood tests, with endocrinology for complex cases. Private endocrinology and GP services offer direct access to thyroid and iron tests.