Understanding a blood test result can feel daunting, particularly when a number falls outside the expected range. If you have recently received a serum folate result that appears elevated — or if you are simply trying to understand what a folic acid lab test actually measures — this article is designed to help. It explains what the test looks at, why results vary, what high folate levels may or may not indicate, and when speaking with a healthcare professional would be a sensible next step.
This article is intended as general health information only. It does not replace personalised medical advice, diagnosis or treatment.
What Is a Folic Acid Lab Test?
A folic acid lab test — more precisely referred to as a serum folate test — measures the concentration of folate (vitamin B9) circulating in the bloodstream at the time of sampling. It is one of the standard ways to assess a person's folate status and is often requested alongside a full blood count or vitamin B12 measurement.
In a laboratory report, serum folate is sometimes abbreviated as SFOL or labelled as "serum folate" or "folic acid (serum)". If you see any of these terms on your results printout, they refer to the same test.
It is worth noting that serum folate reflects relatively recent folate intake rather than longer-term body stores. This distinguishes it from red blood cell (RBC) folate testing, which can give a broader picture of folate status over a longer period. Healthcare professionals choose between these tests — or use both — depending on the clinical question being explored.
Folate vs Folic Acid: Is There a Difference?
Yes — though the terms are often used interchangeably, there is a meaningful distinction.
Folate is the naturally occurring form of vitamin B9 found in foods such as leafy green vegetables, legumes, eggs and liver. The body absorbs and processes dietary folate through a series of enzymatic steps in the gut and liver.
Folic acid is the synthetic form of vitamin B9 used in dietary supplements and in the fortification of certain foods such as breakfast cereals and bread products. Folic acid is structurally different from dietary folate and is generally considered to be more stable and more readily absorbed.
Both forms ultimately contribute to folate levels in the body, and standard blood tests do not distinguish between them. This means that high serum folate levels may reflect dietary intake, supplement use, or a combination of both.
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Why Is a Folate Test Requested?
A healthcare professional may request a serum folate test for several reasons, including:
If you are arranging private health screening and would like to understand which tests may be relevant for you, reviewing available test options and prices can be a helpful starting point before speaking with a clinician.
What Do High Folate Levels Mean?
An elevated folate result — sometimes described as raised folate levels, high serum folate or a high folic acid blood test result — is not necessarily a cause for concern, but it does warrant careful interpretation.
The most common reasons for a high serum folate result include:
1. Recent Supplement Use
Folic acid supplements are widely available and commonly taken for general health, preconception care or on medical advice. Taking a folic acid supplement shortly before a blood test — particularly a high-dose one — can significantly raise serum folate levels. This is one of the most frequent explanations for an unexpectedly elevated result.
2. Fortified Food Intake
Many everyday foods, including some breakfast cereals, bread and plant-based milk alternatives, are fortified with folic acid. Regular consumption of multiple fortified products can contribute to elevated serum folate levels, even without taking dedicated supplements.
3. Laboratory and Testing Variation
Different laboratories use different analysers, assay methods and reference ranges. A result that appears elevated at one laboratory might sit within the normal range at another. This is why laboratory reference ranges must always be consulted alongside the numerical result.
4. Timing of the Blood Sample
Because serum folate reflects recent intake rather than long-term stores, eating a folate-rich or folic acid-fortified meal shortly before testing can temporarily elevate the result. Some laboratories recommend fasting before a serum folate test; others do not. Following your laboratory's specific preparation guidance helps ensure the most accurate result.
5. Clinical Conditions
In some clinical situations, elevated serum folate levels may be noted alongside other blood-test findings. However, it would be inappropriate to attribute a specific diagnosis to an elevated folate result without a full clinical assessment. Interpretation should always be carried out by a qualified healthcare professional in context.
Folate Level Greater Than 20: What Does It Mean?
This is a commonly searched question, and the honest answer is: it depends.
A folate level greater than 20 may appear on a report as ">20", "20+" or simply as a number exceeding 20. However, the significance of this result cannot be assessed without knowing:
If your result shows a folate level greater than 20 and you are uncertain what this means for you, the most appropriate step is to discuss it with a GP or other qualified healthcare professional who can review your full results and medical context.
What Are the Symptoms of High Folate Levels?
This is a reasonable question, and the evidence-based answer is nuanced.
There are no well-established, clearly recognised symptoms that are directly and reliably attributed to high serum folate levels in otherwise healthy individuals. Unlike folate deficiency, which is associated with fatigue, mouth sores, and certain changes in blood-cell production, elevated folate from dietary sources or supplementation does not have a clearly defined symptom profile.
Some research has explored whether very high folic acid intake — particularly from supplements over long periods — might interact with vitamin B12 metabolism in certain individuals. However, this is an area of ongoing scientific discussion rather than established clinical consensus, and no specific "symptoms of high folate" have been validated as a reliable clinical indicator.
If you are experiencing symptoms such as fatigue, tingling, difficulty concentrating or other concerns, it is important not to attribute these to a high folate result without proper medical assessment. These symptoms have many potential causes, and a healthcare professional is best placed to investigate them appropriately.
Folate and Vitamin B12: Why Are They Often Tested Together?
Folate and vitamin B12 are closely linked in the body's metabolic processes, particularly those involved in cell division and the production of red blood cells. Because of this relationship, a serum folate test is frequently requested alongside a vitamin B12 test.
One important reason for assessing both together is that folate and vitamin B12 deficiency can produce similar changes in red blood cells — specifically, an increase in cell size known as macrocytosis. Without testing both nutrients, it can be difficult to determine which deficiency, or combination of factors, is responsible.
There is also a clinical consideration regarding high folate intake and vitamin B12 deficiency. Some clinical guidance notes that large amounts of supplemental folic acid may mask certain blood changes associated with vitamin B12 deficiency, potentially delaying its diagnosis. This underlines why folate results are rarely interpreted in isolation.
If you are having a folic acid serum test, it is worth confirming with your healthcare provider whether vitamin B12 should be measured at the same time. A comprehensive health screening panel may include both alongside other relevant markers.
How Is a Serum Folate Test Performed?
The test requires a small blood sample, typically collected from a vein in the arm using a standard venepuncture procedure. This is a straightforward and commonly performed process that takes only a few minutes.
The sample is then sent to a laboratory for analysis, where the concentration of folate in the serum — the liquid component of blood — is measured. Results are usually reported in nmol/L or µg/L, depending on the laboratory.
Some laboratories advise fasting before the test to avoid temporary fluctuations caused by recent food intake. If you are unsure whether to fast before your sample is taken, check the specific guidance provided by the service you are using.
At Private Blood Tests London, blood samples are taken by trained phlebotomists and processed through accredited laboratories. You can book a blood test appointment at a time that suits you.
Understanding Your Blood Test Results
When you receive a serum folate result, it will typically include:
It is important to interpret results using the reference range provided by your specific laboratory, as these can differ between providers. A result slightly outside the reference range does not automatically indicate a clinical problem, and a result within range does not rule out all concerns.
Folate results should be considered alongside other blood markers. For example, a full blood count test may reveal changes in red blood cell size or haemoglobin that add important context to folate findings.
Your healthcare professional will consider your results as part of your broader health picture, including your symptoms, medical history, medication use and lifestyle factors.
When to Seek Medical Advice
You should speak with a GP or other qualified healthcare professional if:
Private blood testing can be a useful and timely way to access results, but it does not replace the clinical assessment, context and professional judgement that a healthcare professional provides.
Frequently Asked Questions
What does a folic acid lab test measure?
A folic acid lab test — formally known as a serum folate test — measures the concentration of folate (vitamin B9) in the liquid part of your blood. It is used to assess your folate status at the time of testing and can help identify whether levels are within, below or above the laboratory's reference range.
Is folate the same as folic acid?
They are closely related but not identical. Folate is the naturally occurring form of vitamin B9 found in food. Folic acid is the synthetic form used in dietary supplements and fortified foods. Both contribute to your overall folate status, and standard blood tests do not distinguish between them.
What does a high folate level mean?
A high or elevated serum folate result most commonly reflects recent supplement use or a diet rich in fortified foods. It may also relate to the timing of the blood sample or variation between laboratories. Elevated results should be interpreted in clinical context by a healthcare professional rather than assumed to indicate a specific condition.
What are the symptoms of high folate levels?
There are no clearly established, reliably recognised symptoms directly attributed to elevated serum folate in otherwise healthy individuals. If you are experiencing unexplained symptoms, these should be assessed by a healthcare professional rather than attributed to a high folate result without investigation.
What does a folate level greater than 20 mean?
The meaning of a result greater than 20 depends on the units used (nmol/L or µg/L), the reference range of the specific laboratory, and your individual clinical context. In some cases, ">20" simply indicates the result exceeded the assay's measurement threshold. A healthcare professional can help interpret what this means for you specifically.
Why would a healthcare professional request a folate test?
A folate test may be requested to investigate possible nutritional deficiency, to assess unexplained changes on a full blood count such as enlarged red blood cells, to monitor people on certain medications, or as part of broader health screening. It is also commonly requested in preconception and early pregnancy assessment.
Can supplements affect serum folate results?
Yes. Taking folic acid supplements — particularly at higher doses — before a blood test can significantly raise serum folate levels. If you are taking supplements, it is worth informing the requesting clinician or the laboratory, as this context is important for interpreting your result.
Why is vitamin B12 often checked alongside folate?
Folate and vitamin B12 work closely together in the body, particularly in red blood cell production and cell division. Deficiencies in either can cause similar blood changes, so testing both together helps clarify the picture. High folate intake may also mask certain signs of vitamin B12 deficiency, making combined testing particularly useful.
What is an SFOL blood test?
SFOL is a laboratory abbreviation used by some reporting systems to denote a serum folate test. If you see SFOL on a blood test request or result form, it refers to the measurement of folate in your serum — the same as a folic acid serum test or serum folate test.
Does a high serum folate result confirm that I am taking too many supplements?
Not necessarily. While supplement use is a common reason for elevated serum folate, results should be interpreted carefully alongside other information. It is always worth discussing supplement use with a healthcare professional to ensure the dose and type are appropriate for your circumstances.
How is a serum folate blood test different from a red blood cell folate test?
Serum folate reflects your recent folate intake and can be influenced by what you have eaten or supplemented in the days before the test. Red blood cell (RBC) folate provides a broader measure of longer-term folate status. Healthcare professionals choose between — or combine — these tests depending on what clinical information is needed.
Can I arrange a private folic acid blood test in London?
Yes. Private blood testing services in London offer serum folate tests, often alongside vitamin B12 and full blood count panels. Private testing can provide quick access to results, though any findings should be discussed with a qualified healthcare professional for proper interpretation and follow-up.
This article is intended for general health information purposes only. It does not constitute medical advice, diagnosis or treatment. Always consult a qualified healthcare professional regarding your individual health circumstances and blood test results.