B Vitamin Deficiency: B1, B2 and B6 Symptoms and the Blood Test

Lab Tests Online UK calls severe B vitamin deficiency rare in the UK, and the NHS says you should be able to get all of the vitamin B1 (thiamin), B2 (riboflavin) and B6 you need from your daily diet.^{3, 1} The symptoms laboratories list, such as a sore tongue, anaemia or tingling in the hands and feet, can be non-specific, and the NHS gives many causes of the tingling, so they cannot confirm a deficiency.^{3, 5} Blood tests exist for each, but 10 UK services print a B6 range, 10 a B1 range and 4 a B2 range, and the figures differ by service and by unit.^{8, 9, 10}

This is general information, not advice on your own symptoms or result.

Contains public sector information licensed under the Open Government Licence v3.0.

How much the NHS says adults need

The NHS says adults aged 19 to 64 need 1 mg of thiamin a day for men and 0.8 mg for women, and about 1.3 mg and 1.1 mg of riboflavin and 1.4 mg and 1.2 mg of vitamin B6.¹ It names peas and nuts as sources of thiamin, milk and eggs of riboflavin, and pork, poultry and bananas of B6.¹ The NHS pages were last reviewed in August 2020, and their next review was due in August 2023.^{1, 2}

What the NHS says about taking too much, especially B6

The NHS says 200 mg or more of vitamin B6 a day can lead to a loss of feeling in the arms and legs, known as peripheral neuropathy.¹ This will usually improve once the supplements are stopped, but in a few cases where people took large amounts, particularly for more than a few months, the effect can be permanent.¹ For 10 mg to 200 mg a day the NHS says the effect is unclear and there is not enough evidence to say how long such doses could be taken safely, and it says not to take more than 10 mg a day in supplements unless a doctor advises it.¹

Symptoms the sources list for low B1, B2 and B6

The symptoms listed for low B1, B2 or B6 can be non-specific and have other causes, so they cannot show a vitamin is the reason.^{3, 5} A Scottish reference laboratory lists:

B1: peripheral neuropathy, muscle pain and tenderness, heart failure, and Wernicke Korsakoff syndrome (abnormal eye movement and gait, confusion and memory loss)⁴
B2: sore throat, inflammation of the mouth, tongue and throat, cracks in the lips and corners of the mouth, anaemia and dermatitis⁴
B6: irritability, depression, confusion, inflammation of the tongue, mouth sores or ulcers, convulsions and anaemia⁴

South Tees, Rotherham and North West London add malaise, weight loss, irritability and confusion for marginal B1 deficiency, and Newcastle, South Tees and Rotherham add skin changes to their B6 list.^{8, 9, 11} For the B vitamins as a group, Lab Tests Online UK adds numbness, tingling or burning in the hands or feet.³ The NHS says diabetes is the commonest cause of peripheral neuropathy in the UK and lists many others, including excessive drinking for years and low levels of vitamin B12 or other vitamins.⁵

Causes of deficiency and who is more likely to be low

The sources point to a poor diet, poor absorption and losses from the body, and name alcohol dependence among the settings where deficiency is seen.^{3, 4}

Alcohol dependence: in the UK, B1 deficiency is found primarily with it³, and South Tees and Rotherham add that alcohol inhibits thiamine absorption⁹
Digestive conditions: malabsorption, coeliac disease, Crohn's disease or gastric bypass surgery^{3, 4}
Malnutrition, older age, kidney dialysis (which increases losses) and severe prolonged vomiting^{3, 4}
Certain medicines, for B6⁴

The Scottish laboratory calls specific B2 deficiency very rare and B6 deficiency rare, usually with other water-soluble vitamin deficiencies.⁴

Which services test for B1, B2 and B6, and the ranges they print

Ten UK services print a B6 range, ten a B1 range and four a B2 range, and the figures differ by service, sample and unit. In October 2026 we opened the page or document of all 16 services we found listing at least one of the three, across England and Scotland. Six (Bristol, North West London, Worcestershire, North Midlands, the Eastern Pathology Alliance and Bath) list a test without a range.¹¹ Leeds, Black Country, Bristol and Worcestershire ask requesters to discuss the test with the laboratory first, and Bristol calls B1 and B6 rarely indicated.^{8, 9, 11} These count services, not independent assays: Edinburgh sends its samples to the Glasgow laboratory.⁸

Vitamin B6 (whole blood pyridoxal phosphate, nmol/L unless stated)⁸:

44 to 168: Sussex, Birmingham and Synnovis (a partnership of SYNLAB UK and Ireland with two NHS trusts)
35 to 110: Rotherham and Newcastle
40 to 100: South Tees
51 to 183: Black Country
Red cell figure, 250 to 680 pmol/g Hb, a different unit: Glasgow, Edinburgh and Leeds

Vitamin B1 (whole blood thiamine diphosphate, nmol/L unless stated)⁹:

66.5 to 200: Leeds, Newcastle, Birmingham, Rotherham and Synnovis (Sussex prints 66 to 200)
50 to 220: Black Country and South Tees
275 to 675 ng/g Hb, a different unit: Glasgow and Edinburgh

Vitamin B2 (riboflavin)¹⁰:

174 to 471 nmol/L: Sussex
Red cell flavin adenine dinucleotide, 1.0 to 3.4 nmol/g Hb: Glasgow, Edinburgh and Leeds

The same result can sit inside the range at one service and below it at another. On the printed ranges alone, not as a comment on anyone's result, a whole blood B6 of 40 nmol/L is inside the range at 3 of the 7 nmol/L services and below it at 4, and a thiamine of 60 nmol/L is below the lower limit at 6 of the 8 nmol/L services and inside it at 2. Black Country and South Tees name Rotherham as their laboratory, yet print 50 to 220 for B1 where Rotherham's own document prints 66.5 to 200, and 51 to 183 and 40 to 100 for B6 where it prints 35 to 110.^{8, 9}

Lab Tests Online UK lists thiamine and pyridoxine (B1 and B6) among the nutrient tests it calls useful only in rare circumstances, because clinically relevant deficiency is unlikely, puts the remaining B vitamins among tests where analysis very rarely brings any benefit, and says micronutrient tests are a valid assessment when symptoms suggest a deficiency.¹²

Sample handling and timing

The services give different instructions on light, timing, fasting and illness or surgery.

Light and delay: most ask for protection from light, such as foil, and Sussex wants the sample at the laboratory within 6 hours.⁸
Illness or surgery: Sussex and Birmingham advise against measuring B6 during a severe acute phase response, such as after surgery, and allowing at least 14 days.⁸ In the Scottish laboratory's study of 20 people after knee surgery, plasma B6 fell by about half and the red cell level did not.⁴
Fasting: Glasgow, Edinburgh and Leeds prefer a fasting sample or one 8 hours after a supplement dose, Birmingham a fasted morning sample, and South Tees needs no preparation.^{4, 8, 9}
Method: a 2018 paper on thiamine deficiency worldwide says there is no readily accessible, widely agreed biomarker of thiamine status.⁷

What follows a low result, and when to see a GP

A low result will not reveal whether the cause is too little in the diet or an inability to absorb or use the vitamin, says Lab Tests Online UK.³ The NHS says to see a GP for pain, tingling or loss of sensation in the feet, loss of balance or weakness.⁵

B1, B2 and B6 in our Vitamin Profile

Our Vitamin Profile lists vitamin B1, B2, B6, B9, B12, vitamin C and vitamin D. Testing at our Mayfair blood testing clinic starts with a complimentary nurse consultation, or you can choose a doctor consultation to decide what to test. A result only makes sense against the range on its own report. B12 and folate have their own guide, B12 blood test levels in the UK, and what a full blood test checks shows where vitamin tests sit.

Common questions

How common is B1, B2 or B6 deficiency in the UK?

We found no UK-wide figure for B1 or B6; Lab Tests Online UK calls severe B vitamin deficiency rare in the UK.³ It says most people have adequate levels and will not need testing. For riboflavin, a 2009 paper on the UK adult National Diet and Nutrition Surveys reports that the share with a red cell marker (EGRAC) of 1.30 or more rose from 2% to 46% of men and from 1% to 34% of women between 1990 and 2003, and found the 1990 method gave significantly lower values.⁶ These are marker values from those surveys, not a current deficiency rate.

Sources

B vitamins and folic acid, NHS, last reviewed August 2020, next review due August 2023
Vitamins and minerals, NHS, last reviewed August 2020, next review due August 2023
B Vitamins, Lab Tests Online UK, viewed October 2026
Scottish Trace Element and Micronutrient Diagnostic and Research Laboratory, Glasgow Royal Infirmary, viewed October 2026: B1 (page); B2 (page); B6 (page); its About page says it is part funded by the National Services Directorate of NHS Scotland
Peripheral neuropathy, NHS, last reviewed October 2022, next review due October 2025: overview and causes
Hill et al., British Journal of Nutrition, 2009, effects of methodological variation on assessment of riboflavin status using the erythrocyte glutathione reductase activation coefficient (EGRAC) assay
Whitfield et al., Annals of the New York Academy of Sciences, 2018, thiamine deficiency disorders: diagnosis, prevalence, and a roadmap for global control programs
Vitamin B6 pages, viewed October 2026: Sussex (page); Birmingham (page); Synnovis (page; partnership described on its About page); Rotherham (document, May 2024); Newcastle (page); South Tees (page); Black Country (page); NHS Lothian, Edinburgh (page); Leeds (page); Glasgow as source 4
Vitamin B1 (thiamine) pages, viewed October 2026: Sussex (page); Leeds (page); Newcastle (page); Birmingham as source 8; Black Country (page); South Tees (page); Rotherham (document, May 2024); Synnovis (page); NHS Lothian, Edinburgh (page); North Midlands (page); Glasgow as source 4
Vitamin B2 (riboflavin) pages, viewed October 2026: Sussex (page); Leeds (page); NHS Lothian, Edinburgh (page); Glasgow as source 4
Services that list a test with no range, viewed October 2026: Bristol, Severn Pathology (B6 and B1); North West London Pathology (B6 and B1); Worcestershire (B1); Eastern Pathology Alliance (B1, B2 and B6); Bath (test list, updated February 2026)
Unvalidated or misleading laboratory tests, Lab Tests Online UK, viewed October 2026