Why am I always cold? Thyroid, low iron and circulation are the usual suspects

Feeling cold when the people around you are comfortable — and finding it is new or persistent rather than just a chilly room — most often points to one of a few ordinary causes. The two to think of first are an under-active thyroid, in which cold intolerance is among the most common symptoms [s1], and iron-deficiency anaemia, the most common type of anaemia, which can leave the hands and feet cold [s2]. A different and more localised pattern — fingers or toes that turn white and then blue in the cold or with stress — is usually Raynaud's phenomenon, a spasm of small blood vessels rather than a whole-body chill [s3].

Distinguishing "cold all over, all the time" from "cold, colour-changing fingers" is the first useful step, because the two point in different directions.

An under-active thyroid

The thyroid sets the body's metabolic thermostat, so when it is under-active, feeling cold is one of the classic complaints. Hypothyroidism is common, and its most frequent symptoms in adults include fatigue, lethargy, cold intolerance, weight gain, constipation, a change in voice and dry skin [s1]. It is readily diagnosed with a blood test and treated with thyroid hormone replacement, though a proportion of treated patients still have lingering complaints [s1]. Because cold intolerance rarely travels alone here, it is the company it keeps — tiredness, weight gain, dry skin — that raises the suspicion. Our report on treating a borderline thyroid covers where the evidence for treatment is strong and where it is not.

Low iron

Iron-deficiency anaemia is the most common form of anaemia, and when it is more than mild it produces the familiar cluster of tiredness, shortness of breath and, notably, cold hands and feet, along with dizziness or light-headedness and pale skin [s2]. The mechanism is straightforward: too little iron means too few healthy red blood cells to carry oxygen, and the extremities feel it first. It is especially worth considering in people with heavy periods or other sources of blood loss, the group our piece on iron deficiency in menstruating women examines. Feeling cold and exhausted together also overlaps heavily with the wider list in why am I always tired.

Raynaud's: cold, colour-changing fingers and toes

When the problem is specifically the fingers or toes — going cold and numb, and changing colour, usually first to white and then to blue — the likely explanation is Raynaud's phenomenon, in which cold temperatures or strong emotions trigger a spasm of the small blood vessels that blocks blood flow to the area [s3]. When blood flow returns, the skin often flushes red. Fingers are most commonly involved, but toes, ears, lips and the nose can change colour too [s3]. In its primary form — occurring on its own — it usually begins in women younger than 30 and is a manageable nuisance [s3]. The version to flag is secondary Raynaud's, which is linked to another condition such as lupus or scleroderma; a first appearance later in life, or attacks that are severe or one-sided, is a reason to be evaluated rather than reassured [s3].

When it is worth checking

New, persistent cold intolerance that comes with fatigue, weight change or dry skin fits an under-active thyroid; cold hands and feet with tiredness, breathlessness or pallor fit anaemia; and both are settled with simple, widely available blood tests [s1][s2]. Colour-changing fingers that begin after age 30, ulcerate, or affect one hand only warrant assessment for a secondary cause [s3]. This article is informational and is not medical advice; it does not diagnose any individual's symptoms or recommend a specific test or treatment.

Sources

• Hypothyroidism — The Lancet, 2017-03-21
• Iron-deficiency anemia — National Heart, Lung, and Blood Institute
• Raynaud phenomenon — MedlinePlus, U.S. National Library of Medicine