Folate Serum (Vitamin B9) Biomarker Testing
It measures vitamin B9 in your blood to help assess deficiency risk and anemia causes, with convenient ordering and Quest-based lab access via Vitals Vault.
With Vitals Vault, you have access to a comprehensive range of biomarker tests.
A Folate Serum test measures the amount of folate (vitamin B9) circulating in your blood at the time of the draw. Folate is essential for making DNA and red blood cells, so low levels can show up as fatigue, mouth sores, or anemia-related symptoms.
This test is most useful when you are trying to explain abnormal blood counts (especially large red blood cells) or when your diet, medications, or absorption issues could be lowering folate. It can also help you and your clinician decide whether folate intake is adequate, and whether follow-up testing is needed.
Because folate and vitamin B12 problems can look similar on routine bloodwork, serum folate is often interpreted alongside other labs rather than in isolation.
Do I need a Folate Serum test?
You may want a Folate Serum test if you have symptoms or lab findings that can fit with folate deficiency, such as persistent fatigue, weakness, shortness of breath with exertion, pale skin, mouth ulcers, or a sore tongue. Another common reason is a complete blood count (CBC) showing macrocytosis (larger-than-usual red blood cells) or anemia that does not have an obvious cause.
Testing can also be helpful if your diet is low in folate-rich foods, if you drink heavily, or if you have conditions that can reduce absorption (for example, chronic gastrointestinal inflammation or prior bariatric surgery). Certain medications can interfere with folate metabolism or absorption, so a folate level can add clarity when medication history and symptoms do not fully match.
If you are pregnant or trying to conceive, folate status matters because folate supports early fetal development. However, a serum folate result is only one piece of the picture, and it does not replace prenatal care or clinician-guided recommendations.
A lab result can support clinician-directed care, but it cannot diagnose the cause of symptoms by itself. If your folate is low, the next step is usually to confirm the pattern with related tests and identify why it is low, not just to “treat the number.”
This is a CLIA laboratory blood test; results should be interpreted in clinical context and are not a standalone diagnosis.
Lab testing
Order a Folate Serum test and view results in your Vitals Vault dashboard
Schedule online, results typically within about a week
Clear reporting and optional clinician context
HSA/FSA eligible where applicable
Get this test with Vitals Vault
If you are deciding whether to check folate, Vitals Vault lets you order the Folate Serum test and complete your blood draw through a national lab network. You can use the result to have a more specific conversation with your clinician, especially if you are trying to explain anemia, macrocytosis, or nutrition concerns.
Once your result is back, PocketMD can help you make sense of what “low,” “in range,” or “high” typically means, and which companion labs often add the most clarity (such as vitamin B12, methylmalonic acid, homocysteine, and a CBC). That way, you are not left guessing whether you should retest, expand testing, or focus on diet and absorption.
If you are monitoring a known deficiency or checking response after changes in diet or supplementation, you can also use Vitals Vault to trend results over time and keep your lab history in one place.
- Order online and complete testing through a national lab network
- PocketMD guidance for follow-up questions and next-step labs
- Designed for repeat testing so you can track changes over time
Key benefits of Folate Serum testing
- Helps evaluate whether low folate could be contributing to macrocytosis or anemia patterns on a CBC.
- Adds context when symptoms like fatigue, mouth sores, or a sore tongue do not have an obvious explanation.
- Supports nutrition assessment when diet quality, alcohol use, or restricted eating may limit folate intake.
- Helps identify when folate status should be interpreted alongside vitamin B12 to avoid missing a B12 problem.
- Provides a baseline before and after diet changes or clinician-directed supplementation to confirm response.
- Can guide whether additional tests (homocysteine, methylmalonic acid) are likely to clarify the cause of abnormal results.
- Makes it easier to trend folate status over time with consistent ordering and PocketMD interpretation support.
What is Folate Serum?
Folate is the natural form of vitamin B9 found in foods, while folic acid is the synthetic form used in many supplements and fortified foods. Your body uses folate to build and repair DNA, to support rapid cell turnover, and to make healthy red blood cells.
A Folate Serum test measures folate circulating in your bloodstream. Because serum levels can change with recent intake, this test is best interpreted with your overall clinical picture, your diet and supplement history, and your blood counts.
Folate and vitamin B12 work closely in pathways that affect red blood cell production and homocysteine metabolism. That is why clinicians often look at folate and B12 together when macrocytosis or anemia is present.
Serum folate vs. red blood cell (RBC) folate
Serum folate reflects what is available in the blood right now and can rise after a folate-rich meal or supplement. RBC folate reflects folate stored in red blood cells and may better represent longer-term status in some situations. Many clinicians start with serum folate because it is widely available, then consider additional testing if the story is unclear.
Why folate matters for blood counts
When folate is low, the bone marrow can struggle to produce normal red blood cells. This can lead to megaloblastic changes and macrocytosis, sometimes before anemia becomes severe. A folate result can help explain why red blood cell indices (like MCV) are abnormal.
What do my Folate Serum results mean?
Low folate levels
A low serum folate result suggests you may not be getting enough folate, not absorbing it well, or using it up faster than usual. In practice, low folate is often evaluated alongside a CBC to see whether macrocytosis or anemia is present, and alongside vitamin B12 because the two deficiencies can overlap. If you have neurologic symptoms (numbness, tingling, balance issues), your clinician will usually prioritize ruling out vitamin B12 deficiency, because folate can improve anemia while B12-related nerve injury continues.
Optimal (in-range) folate levels
An in-range folate level generally means your current circulating folate is adequate, especially if your CBC is normal and you are not having symptoms suggestive of deficiency. If macrocytosis or anemia is still present, your clinician may look for other causes such as vitamin B12 deficiency, thyroid disease, liver disease, alcohol effects, or certain medications. If you recently started a supplement, an in-range result may reflect recent intake even if longer-term stores were previously low.
High folate levels
A high serum folate result is most commonly due to supplements or fortified foods and is not usually harmful by itself. The main clinical concern is context: high folate can sometimes coexist with low vitamin B12, and focusing only on folate can delay recognition of a B12 problem. If your folate is high and you have anemia, macrocytosis, or neurologic symptoms, it is reasonable to review B12-related testing with your clinician.
Factors that influence folate results
Recent meals and supplements can raise serum folate, so timing and supplement use matter when you interpret the number. Malabsorption conditions, heavy alcohol use, and increased needs (such as pregnancy) can lower folate over time. Several medications can affect folate pathways, and chronic inflammation or liver disease can complicate interpretation through effects on blood counts. Because reference ranges vary by lab and method, it helps to compare your result to the range printed on your report and to trend results using the same lab when possible.
What’s included
- Folate, Serum
Frequently Asked Questions
Do I need to fast for a Folate Serum test?
Fasting is not always required for serum folate, but recent food or supplements can affect the result. If you want the cleanest comparison over time, try to test under similar conditions each time and tell your clinician what supplements you took and when.
What is a normal folate level on bloodwork?
“Normal” depends on the laboratory method and the reference range printed on your report. Your clinician will interpret your value relative to that range and your CBC, symptoms, diet, and vitamin B12 status.
What symptoms can low folate cause?
Low folate can contribute to fatigue, weakness, shortness of breath with exertion, pale skin, mouth sores, and a sore or smooth tongue. Some people have no clear symptoms until anemia or macrocytosis shows up on a CBC.
Is serum folate the same as folic acid?
Serum folate measures folate circulating in your blood. Folic acid is a synthetic form of vitamin B9 found in many supplements and fortified foods; it can raise serum folate levels, sometimes quickly.
Should I test vitamin B12 if my folate is low or high?
Often, yes. Folate and vitamin B12 deficiencies can look similar on a CBC, and high folate from supplements can coexist with low B12. Many clinicians check B12 (and sometimes methylmalonic acid and homocysteine) when folate results are abnormal or when macrocytosis/anemia is present.
How soon should I retest folate after changing diet or starting supplements?
Serum folate can change relatively quickly, but the right retest timing depends on why you are testing and what else is abnormal. A common approach is to recheck in several weeks to a few months, along with a CBC and any companion tests your clinician recommends, to confirm the pattern is improving.
Can medications affect folate levels?
Yes. Some medications can interfere with folate absorption or metabolism, which can contribute to low levels or anemia patterns. If your result is abnormal, review your medication list with your clinician before making changes.