Blood Tests for Anxiety: Ruling Out Physical Causes

Anxiety is a feeling of unease, such as worry or fear, that everyone has at times. When it is constant or hard to control, it can affect sleep, work and relationships, and it often comes with physical symptoms such as a racing or pounding heart, sweating, trembling, dizziness and stomach problems. Some of these overlap with physical conditions that a blood test can pick up, such as an overactive thyroid or anaemia.

This guide covers the blood tests most worth checking when you feel anxious, which panel to choose, what blood tests cannot tell you and when to get urgent help. Anxiety itself is diagnosed by talking with a GP or mental health professional, not with a blood test. Your result is a starting point for a conversation, not a diagnosis.

Test it in Chiswick: our Thyroid blood test costs £59, with your result explained in person by a practitioner. No GP referral needed. Book this test or call 020 4515 0000. Prefer to test at home? A home finger-prick kit is also available, ask us when you enquire.

Quick answer

No blood test can diagnose anxiety, but a few can find physical problems that cause similar symptoms or make anxiety worse. The most useful is a thyroid test, because the NHS lists nervousness, anxiety, irritability, a fast heartbeat, sweating and poor sleep among the symptoms of an overactive thyroid. HbA1c checks blood sugar, a full blood count and ferritin look for anaemia, and vitamin B12, vitamin D and calcium are often added. Cortisol is only useful when there are signs of a hormone condition. Chest pain that does not go away needs 999, not a blood test.

Blood tests that can help

Thyroid function, especially an overactive thyroid

An overactive thyroid (hyperthyroidism) speeds up many of the body's processes. The NHS lists nervousness, anxiety and irritability, hyperactivity, mood swings, difficulty sleeping, an irregular or unusually fast heart rate, trembling, sweating and weight loss among its symptoms, and says a GP can arrange a blood test to check whether the thyroid is the cause. Our Thyroid test (£59) measures TSH, free T4, free T3 and two thyroid antibodies. A low TSH with a high free T4 or free T3 suggests an overactive thyroid. Our thyroid results guide explains the patterns, and you can read more about overactive thyroid symptoms.

Blood sugar: HbA1c and glucose

The NHS lists feeling anxious or irritable, sweating, shaking and palpitations as symptoms of low blood sugar (hypoglycaemia). This mainly affects people with diabetes who use insulin or tablets such as gliclazide, and it is rare in people without diabetes. If you have diabetes and these symptoms, check your blood sugar and treat a low straight away. An HbA1c test (£59) shows your average blood sugar over the past two to three months, and a Glucose test costs £39.

Full blood count and ferritin

Iron deficiency anaemia can cause tiredness, shortness of breath, headaches and noticeable heartbeats (palpitations), which can feel very like anxiety. A Full Blood Count (£59) checks haemoglobin and red cells, and a Ferritin test (£49) shows your iron stores. See our guide to ferritin levels.

Vitamin B12

The NHS lists psychological problems, ranging from mild depression or anxiety to confusion, among the symptoms of vitamin B12 deficiency, along with palpitations, tiredness and pins and needles. Our Vitamin B12 test costs £49, and our vitamin B12 guide explains the results.

Vitamin D: a balanced view

Low vitamin D is common in the UK, especially from October to March, and it is often checked in a wider screen. However, studies on vitamin D and anxiety have mixed results, and there is no good evidence that low vitamin D causes anxiety or that supplements treat it. The NHS advises everyone to consider 10 micrograms of vitamin D a day in autumn and winter. A Vitamin D test costs £59.

Calcium

High calcium, most often caused by an overactive parathyroid gland, can cause low mood, tiredness, thirst and passing more urine. Low calcium can cause tingling and muscle cramps or spasms, which can be mistaken for a panic attack. An Adjusted Calcium test costs £49. See our guide to calcium levels.

Cortisol: only where there is a reason

Cortisol is often called the stress hormone, but a blood cortisol test cannot measure how stressed or anxious you are, and it changes a great deal through the day. It is useful when there are other signs of a cortisol problem. The NHS lists feeling irritable, anxious or depressed among the symptoms of Cushing's syndrome, alongside weight gain on the tummy, face, neck and upper back, a round red face, easy bruising, stretch marks and muscle weakness. The most common cause is taking high-dose steroid medicine. Cortisol is best tested at about 9am. Read more in our cortisol levels guide.

Which test should I book?

• A focused start: Thyroid, £59. TSH, free T4, free T3 and two thyroid antibodies. The best single first test, especially if anxiety comes with a racing heart, trembling, sweating, feeling hot or weight loss.
• A broader picture: Stress Hormone Check, £79. Cortisol and DHEA-S from a morning sample. Suited to people with signs of a cortisol problem as well as anxiety. It does not diagnose anxiety or measure stress.
• The fullest view: Tired All The Time, £159. A full thyroid profile with antibodies, full blood count, ferritin and iron studies, vitamin B12, folate, vitamin D, HbA1c, glucose, calcium, magnesium, kidney function and CRP in one sample. It covers most of the physical causes in this guide, although not cortisol.

What blood tests cannot tell you

Anxiety is diagnosed clinically. A GP will ask about your worries and physical symptoms, and the NHS says generalised anxiety disorder may be diagnosed if you have felt anxious a lot of the time for at least 6 months. For panic disorder, a GP may examine you to rule out other conditions. Blood tests only look for physical contributors.

Normal results are common and still useful. Many things that drive anxiety do not show in blood at all, including stress, poor sleep, caffeine, alcohol, some medicines and recreational drugs. Normal results do not mean your symptoms are not real. They help you and your GP focus on what is left, including talking therapies, which work well for many people. Read more about anxiety symptoms. If you would like support alongside your GP care, see our stress and anxiety care at Omnia.

When to get help urgently

Call 999 if you have sudden chest pain or discomfort that does not go away, pain that spreads to your arm, neck, jaw, stomach or back, or chest pain with sweating, feeling sick, light-headedness or shortness of breath. Anxiety and panic attacks can cause chest pain, but do not assume that is the cause.

If you have thoughts of harming yourself or ending your life, or feel you cannot keep yourself safe, get help now:

• Call NHS 111 and choose the mental health option (option 2 in England), available 24 hours a day.
• Call Samaritans free on 116 123, at any time of day or night.
• Call 999 or go to A&E if your life is at risk, for example if you have seriously injured yourself or taken an overdose.

Book a GP appointment if anxiety is affecting your daily life, you have panic attacks, or you notice weight loss, a racing heart at rest or a swelling in your neck. Adults can also refer themselves directly to NHS talking therapies without seeing a GP.

Frequently asked questions

Can a blood test detect anxiety?

No. Anxiety is diagnosed from your symptoms and history. Blood tests look for physical causes of similar symptoms, such as an overactive thyroid or anaemia.

Can thyroid problems cause anxiety?

Yes. An overactive thyroid commonly causes nervousness, irritability, a fast heartbeat, trembling and poor sleep. A thyroid blood test is the most useful first check.

Can low B12 cause anxiety?

The NHS lists anxiety among the psychological symptoms of B12 deficiency, so it is worth checking, especially with tiredness or pins and needles.

Should I have my cortisol tested for anxiety?

Usually not on its own. Cortisol is helpful when there are signs of a cortisol problem, such as those of Cushing's syndrome, and it cannot measure how anxious you are.

What if all my blood tests are normal?

That is common and reassuring. Your practitioner can talk through sleep, caffeine, alcohol and stress, and your GP or an NHS talking therapies service can help with treatment.

Anxiety blood testing in Chiswick

We take your sample at our clinic at 8 to 9 Bedford Corner, The Avenue, Chiswick, London W4 1LZ. We are a short walk from Turnham Green station (District line, with Piccadilly line trains stopping there early morning and late evening only) and close to the 94, E3 and 272 bus routes. Limited parking is available on request when you book. Your sample is analysed at the Randox accredited laboratory, no GP referral is needed, and most results are ready within a few working days. A practitioner explains your result with you in person, and a GP feedback report is available on request.

Book the Thyroid blood test, choose the wider Tired All The Time panel, or compare every blood test and price. You may also find our guides to thyroid test results and cortisol levels helpful.

This article is general information, not medical advice. Discuss your results with your GP or practitioner.