Pantothenic Acid (Vitamin B5) Unit Converter
Pantothenic Acid (Vitamin B5) Unit Converter
Convert pantothenic acid between mg/L, µg/L, ng/mL and µmol/L — and read the result knowing that isolated vitamin B5 deficiency is essentially unknown in humans and the test is very rarely indicated.
Pantothenic Acid (Vitamin B5) converter
Mass ⇄ molarSerum pantothenic acid 80 µg/L
The conversion
µg/L = ng/mL, and 1 mg/L = 1,000 µg/L
because 4.56142 = 1 mg/L ÷ 219.23 g/mol, the molecular weight of pantothenic acid
- MW 219.23
- pantothenic acid, C₉H₁₇NO₅. Only the D-(+) enantiomer is biologically active; supplements usually contain calcium pantothenate or the alcohol panthenol, both of which are converted to it
- µg/L = ng/mL
- identical concentrations. Serum B5 is reported in the tens to low hundreds of µg/L, which is why the page opens in that unit rather than in its base mg/L
- what is actually measured
- free pantothenic acid in serum or whole blood. The great majority of the body's pantothenate is inside cells as coenzyme A and as the acyl carrier protein prosthetic group, neither of which the assay sees
- the assay
- most laboratories use a microbiological bioassay — growth of a pantothenate-dependent organism such as <i>Lactobacillus plantarum</i> — rather than mass spectrometry. Values are not transferable between methods
Worked example
Serum pantothenic acid 80 µg/L
80 µg/L = 80.0 ng/mL = 0.0800 mg/L
0.0800 × 4.56142 = 0.36 µmol/L, or 365 nmol/L
80 µg/L is inside Mayo's 37–147 µg/L interval for over-10s, which is 0.17–0.67 µmol/L
Going back: 0.36 ÷ 4.56142 = 0.079 mg/L = 79 µg/L, the rounding of the displayed 0.36 accounting for the last unit
The more useful question is why the test was sent. Pantothenic acid is present in nearly every food — the name is from the Greek for "from everywhere" — and isolated deficiency has essentially only been produced experimentally
What is known about pantothenic acid deficiency in humans
| Evidence | What it showed |
|---|---|
| Experimental depletion studies, using a pantothenate-free diet or the antagonist ω-methylpantothenic acid | Produced burning feet, headache, fatigue, irritability, numbness and impaired coordination — reversed by pantothenate. This is essentially the whole of the human deficiency syndrome, and it had to be manufactured |
| “Burning feet syndrome” in prisoners of war in the Second World War | Attributed to pantothenate deficiency in some accounts, but occurring against severe generalised malnutrition, so it cannot be assigned to B5 alone |
| Naturally occurring isolated deficiency | Not described. Pantothenic acid occurs in almost all plant and animal foods, and the gut microbiota synthesise it |
| Deficiency as part of generalised undernutrition | Can be demonstrated biochemically, but it is not what makes the patient ill and it is not what is treated first |
Where the pantothenate actually is
| Pool | Form | Seen by the serum assay? |
|---|---|---|
| Intracellular, the large majority | Coenzyme A | No |
| Intracellular | 4′-phosphopantetheine on acyl carrier protein, in fatty-acid synthase | No |
| Whole blood | Mostly as CoA within red cells | Only if whole blood is assayed after hydrolysis |
| Serum or plasma | Free pantothenic acid | Yes — and this is the fraction that moves with recent intake |
A vitamin named for being everywhere
Pantothenic acid converts from milligrams per litre to micromoles per litre by multiplying by 4.56142, from its molecular weight of 219.23 grams per mole. Because laboratories report serum B5 in the tens to low hundreds of micrograms per litre — the same number as nanograms per millilitre — the page opens in that unit rather than in the milligrams per litre the factor is defined against.
The more important point is about indication. Pantothenic acid takes its name from the Greek pantothen, meaning “from everywhere”, and the name is accurate: it is present in almost every plant and animal food, meat, eggs, wholegrains, legumes and vegetables among them, and the gut microbiota make more. Isolated deficiency has essentially never been described as a naturally occurring condition in a person with access to food. What is known about the deficiency syndrome comes from experimental depletion — volunteers fed a pantothenate-free diet, sometimes with the antagonist ω-methylpantothenic acid — in whom burning feet, headache, fatigue, irritability, numbness and impaired coordination appeared and resolved on repletion. The burning-feet syndrome reported among prisoners of war in the Second World War is often cited as a natural example, but it arose against severe general malnutrition and cannot be attributed to one vitamin.
The practical consequence is that a serum pantothenic acid is rarely the right test. Where it is genuinely low, it is almost always one finding within generalised undernutrition or a broad multiple-vitamin deficiency — the patient’s problem, and the thing to treat, is the undernutrition. A high value almost always means a supplement: pantothenate is in most multivitamin preparations, often at many times the adequate intake of about 5 mg a day, and no toxicity syndrome is recognised beyond loose stools at very large doses.
Two technical caveats are worth carrying. First, the assay in common use is a microbiological bioassay, measuring the growth of a pantothenate-dependent organism, rather than mass spectrometry — results are method-dependent and not transferable between laboratories, and the reference interval printed here belongs to one named bioassay. Second, the serum measures free pantothenic acid, while almost all of the body’s pantothenate is held inside cells as coenzyme A and as the 4′-phosphopantetheine arm of acyl carrier protein. Whole-blood pantothenate tracks intake better than serum does, and neither is a validated measure of functional status.
Frequently asked questions
How do you convert pantothenic acid from mg/L to µmol/L?
Multiply by 4.56142, which is one milligram per litre divided by pantothenic acid’s molecular weight of 219.23 g/mol. Because laboratories report B5 in micrograms per litre — the same number as nanograms per millilitre — it is usually easier to divide the µg/L figure by 1,000 first. A serum B5 of 80 µg/L is 0.36 µmol/L, or 365 nmol/L.
Is vitamin B5 deficiency a real condition?
In isolation, essentially not. Pantothenic acid is present in almost all foods and is also made by the gut microbiota, and naturally occurring isolated deficiency has not been described. The human deficiency syndrome — burning feet, headache, fatigue, irritability, numbness, impaired coordination — was produced experimentally with a pantothenate-free diet and an antagonist. Where a low level turns up clinically it is generally part of broader undernutrition.
When is a pantothenic acid level actually indicated?
Rarely. It has a place in investigating an unexplained multiple-vitamin deficiency, in research, and occasionally in a specific metabolic question. It is not a sensible component of a routine nutritional screen, and a mildly low result in a patient who is otherwise eating is much more likely to reflect the assay and recent intake than a clinically meaningful deficiency.
Can you take too much vitamin B5?
No toxicity syndrome is recognised. No tolerable upper intake level has been set, and the adverse effect described at very high supplemental doses is loose stools or mild gastrointestinal upset. A high measured level almost always simply means the patient is taking a multivitamin.
Why do results differ between laboratories?
Because most measure pantothenate by a microbiological bioassay — the growth of a pantothenate-dependent organism — rather than by mass spectrometry, and bioassay results are strongly method-dependent. Reference intervals belong to the assay that produced them, so compare a result only with the interval printed on the same report.
Related calculators
References
- Mayo Clinic Laboratories. Test ID: FPAB — Vitamin B5 (Pantothenic Acid) Bioassay. Reference values: over 10 years 37–147 µg/L; 1–10 years 3.45–229.2 µg/L; under 1 year 3.45–825 µg/L.
- Institute of Medicine. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline. Washington DC: National Academies Press; 1998. Pantothenic acid chapter — adequate intake 5 mg/day; no tolerable upper intake level set.
- Hodges RE, Ohlson MA, Bean WB. Pantothenic acid deficiency in man. J Clin Invest. 1958;37(11):1642–1657.
- Fry PC, Fox HM, Tao HG. Metabolic response to a pantothenic acid deficient diet in humans. J Nutr Sci Vitaminol. 1976;22(4):339–346.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.