Folic Acid Oral Solution

Folic acid is a form of vitamin B9 that plays an essential role in red blood cell production, DNA synthesis, and cell division throughout the body. Folic acid oral solution at 2.5 mg/5 ml is a prescription-only liquid formulation of folic acid used in adults and children for the treatment and prevention of folate deficiency anaemia and as pregnancy support for women at higher risk of neural tube defects. Available in two formulations, a standard syrup and a sugar-free version, the liquid form is particularly suitable for patients who have difficulty swallowing tablets or require precise dose measurement. A prescription is required for this formulation.

Folic acid oral solution is a liquid prescription medicine containing folic acid (also known as vitamin B9 or folate in its natural form) as the active ingredient. The concentration is 2.5 mg per 5 ml. It is available in two formulations through this service: a standard syrup containing sucrose, and a sugar-free version suitable for patients who need to avoid sugar, including those with diabetes, phenylketonuria, or sucrose intolerance.

Folic acid belongs to the B-vitamin group and is an essential nutrient for the body. The licensed indications for folic acid 2.5 mg/5 ml oral solution include: treatment of folate deficiency megaloblastic anaemia; prophylaxis of folate deficiency in conditions with increased folate requirements such as haemolytic anaemia and renal dialysis; prophylaxis during pregnancy in women at higher risk of having a baby with a neural tube defect (including women taking certain medicines such as antiepileptics); and as an adjunct to methotrexate therapy to reduce folate depletion side effects.

Folic acid at lower doses (400 mcg) is widely available as an over-the-counter supplement recommended for all women planning a pregnancy. The 2.5 mg/5 ml oral solution is a higher-dose prescription formulation for specific clinical indications requiring therapeutic doses rather than nutritional supplementation alone.

Folic acid is converted in the body to its active form, tetrahydrofolate, which participates in essential biological processes.

DNA Synthesis Support and Cell Division

Folic acid is converted to tetrahydrofolate (THF) and its derivatives after absorption. THF is a coenzyme required for the synthesis of purines and thymidine, the building blocks of DNA. Without adequate folate, cells cannot replicate their DNA efficiently during cell division. This impairs the production of rapidly dividing cells, particularly red blood cells produced in the bone marrow, which divide and mature very frequently.

Red Blood Cell Production and Anaemia Prevention

In folate deficiency, red blood cell precursors in the bone marrow cannot divide and mature normally. They enlarge abnormally, producing large immature red blood cells called megaloblasts. These cells cannot function properly as oxygen carriers. The result is megaloblastic anaemia, characterised by fatigue, breathlessness, and pallor. Folic acid supplementation restores the availability of THF for DNA synthesis, allowing red blood cells to develop and mature normally. This supports healthy red blood cell production and resolves or prevents the anaemia.

Neural Tube Development and Maternal Health

Folic acid plays a critical role in the early development of the fetal neural tube, the structure that forms the brain and spinal cord. Adequate folate in the weeks before and immediately after conception supports normal neural tube closure. Folate deficiency in this period is associated with an increased risk of neural tube defects such as spina bifida and anencephaly. Supplementation with higher-dose folic acid (5 mg daily) is recommended by NHS guidance for women at higher risk of having an affected pregnancy, as part of prenatal supplement and maternal health support.

Always take folic acid oral solution exactly as your prescriber instructs. The information below summarises key points from the current UK SmPC. Read the Patient Information Leaflet supplied with your medicine before starting treatment.

• Measure each dose carefully using the measuring device supplied with the bottle. Do not use a household teaspoon, as this may give an inaccurate dose.
• Folic acid oral solution can be taken with or without food.
• Take the solution at the same time each day to maintain consistent folate levels.
• The dose varies by indication. Your prescriber will specify the dose and duration appropriate for your clinical situation. See the dosage section below for reference.
• If you miss a dose, take it as soon as you remember. If your next dose is due soon, skip the missed dose and continue as normal. Do not double up doses.
• Do not stop taking folic acid oral solution without speaking to your prescriber, as the underlying condition may require ongoing treatment.
• If you are taking folic acid alongside methotrexate therapy, your prescriber will specify exactly when to take folic acid in relation to your methotrexate dose. This timing is important and will be specified individually.

Both formulations of folic acid oral solution available through this service contain the same active ingredient at the same concentration: 2.5 mg folic acid per 5 ml. The dose is measured in millilitres (ml) and the folic acid content of each dose depends on the volume taken.

Folic Acid 2.5 mg/5 ml Oral Solution — Syrup

The syrup formulation contains sucrose as an excipient. It is not suitable for patients who need to avoid sugar. The standard concentration means that 5 ml provides 2.5 mg of folic acid. A 10 ml dose provides 5 mg of folic acid, which is the standard therapeutic dose for high-risk pregnancy prophylaxis and treatment of folate deficiency anaemia in adults. Doses for children are lower and calculated by body weight per prescriber guidance.

Folic Acid 2.5 mg/5 ml Oral Solution — Sugar Free

The sugar-free formulation contains no sucrose and is suitable for patients with diabetes, those following a low-sugar diet, and patients with sucrose intolerance. It provides the same 2.5 mg folic acid per 5 ml. Patients who require the sugar-free version should ensure their prescription specifically states the sugar-free formulation. The clinical indications, dosing, and instructions are identical to the syrup formulation.

Reference Doses by Indication (per current UK SmPC and BNF)

• Treatment of folate deficiency megaloblastic anaemia in adults: 5 mg (10 ml) daily for 4 months, or until term in pregnancy-related deficiency.
• Prevention of first occurrence of neural tube defects (high-risk women): 5 mg (10 ml) daily from at least 4 weeks before conception through to week 12 of pregnancy.
• Prophylaxis during haemolytic anaemia or renal dialysis: typically 5 mg (10 ml) every 1 to 7 days depending on the underlying condition.
• Adjunct to methotrexate: typically 5 mg (10 ml) once weekly, on a day different from methotrexate. Timing and dose specified by the prescriber.

All doses are determined by the prescriber. Do not adjust your dose without medical advice.

Folic acid is generally very well tolerated. Serious side effects are uncommon at therapeutic doses. The information below is based on the current UK SmPC. Refer to the Patient Information Leaflet for the full list.

Uncommon Side Effects

• Gastrointestinal effects such as nausea, bloating, or loss of appetite, particularly at higher doses.
• Sleep disturbances.
• Irritability.

Important Note: Masking Vitamin B12 Deficiency

Folic acid supplementation can improve the blood picture in vitamin B12 deficiency (pernicious anaemia), masking the haematological signs while the underlying B12 deficiency and its neurological complications progress undetected. This is a clinically significant risk. Folic acid must not be started without first excluding or treating vitamin B12 deficiency. Your prescriber will check B12 levels before initiating folic acid treatment for anaemia.

Serious Side Effects: Seek Urgent Medical Attention

Go to your nearest accident and emergency department or call 999 immediately if you experience:

• Signs of a severe allergic reaction such as sudden swelling of the face, lips, tongue, or throat, or difficulty breathing.

Report any suspected side effect to your prescriber, pharmacist, or via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Folic Acid Oral Solution May Be Suitable If You:

• Have been diagnosed with folate deficiency or folate deficiency megaloblastic anaemia.
• Are a woman at higher risk of a neural tube defect-affected pregnancy (including women taking antiepileptic medicines, women with a BMI above 30, women with a previous pregnancy affected by a neural tube defect, or those with diabetes or coeliac disease) and require higher-dose folic acid supplementation as pregnancy support.
• Have haemolytic anaemia or are on renal dialysis and require ongoing folate prophylaxis.
• Are taking methotrexate and require folic acid to reduce folate-related side effects.
• Have difficulty swallowing tablets and require a liquid formulation.
• Have diabetes or sugar intolerance and require the sugar-free formulation.

Folic Acid Oral Solution Requires Care If You:

• Have vitamin B12 deficiency or pernicious anaemia. Folic acid must not be used to treat anaemia until vitamin B12 deficiency has been excluded, as it can mask B12 deficiency and allow neurological damage to progress.
• Have folate-dependent malignant disease. High-dose folic acid may theoretically promote tumour cell growth in some folate-sensitive cancers. Prescribers will assess the risk-benefit balance in these situations.
• Are taking medicines that interact with folate metabolism — see the interaction notes below.

Tell your prescriber about all medicines you take. Key interactions for folic acid include:

• Methotrexate: methotrexate works partly by blocking folate metabolism. Folic acid supplements reduce some methotrexate side effects but must be timed carefully to avoid reducing methotrexate efficacy. Do not take folic acid on the same day as methotrexate unless specifically instructed.
• Antiepileptic medicines (phenytoin, phenobarbital, primidone, carbamazepine): folic acid can reduce serum levels of some antiepileptic medicines. Blood levels of the antiepileptic should be monitored when folic acid is started or stopped.
• Sulfasalazine: reduces folic acid absorption.
• Colestyramine and bile acid sequestrants: may reduce folic acid absorption.

Your prescriber will review your current medicines before prescribing.

Folic acid 2.5 mg/5 ml oral solution is a Prescription Only Medicine at this strength. The clinical consultation is the essential first step. A prescription will only be issued if a registered prescriber concludes, based on their individual assessment of your circumstances, that this formulation is clinically appropriate for you.

During your online consultation with Pharmacy Planet, a registered prescriber will review the information you provide. This includes your clinical indication for folic acid, vitamin B12 status if relevant, current medicines, and whether the syrup or sugar-free formulation is appropriate for your needs. The prescriber will confirm the correct dose and duration for your indication.

Not all consultations will result in a prescription. The prescriber may recommend a different folic acid product for your indication, request blood test results to confirm folate or B12 status, or advise that a face-to-face consultation with your GP is needed. This process is designed to protect your safety.

Store below 25°C. Store in the original bottle. Keep the bottle tightly closed. Keep out of direct sunlight. Keep out of the sight and reach of children. Do not use after the expiry date printed on the label. Check the Patient Information Leaflet for specific shelf life after opening, as some oral solutions have a limited in-use shelf life once the bottle has been opened. Do not dispose of medicines via household waste or wastewater. Return unused or out of date solution to your pharmacist for safe disposal. Full storage instructions are provided in the Patient Information Leaflet supplied with your medicine.

Pharmacy Planet is a GPhC-registered online pharmacy providing access to prescription medicines through a clinically led consultation process. Our registered prescribers and pharmacists are committed to patient safety, clinical accuracy, and responsible prescribing. We follow GPhC standards, MHRA guidance, and ASA advertising regulations in all aspects of our service. Every prescription is reviewed and dispensed by qualified healthcare professionals. We provide clear, factual information about vitamins and nutrient support medicines to help patients make informed decisions about their health. If you have questions about folic acid oral solution or any other medicine, our pharmacy team is available to help. We are committed to transparent, patient centred care.

References

1. Electronic Medicines Compendium (eMC). Folic Acid 2.5 mg/5 ml Oral Solution — Summary of Product Characteristics. https://www.medicines.org.uk/emc. Accessed May 2026.
2. NHS. Folic acid. https://www.nhs.uk/medicines/folic-acid. Accessed May 2026.
3. NHS. Vitamins, supplements and nutrition in pregnancy. https://www.nhs.uk/pregnancy/keeping-well/vitamins-supplements-and-nutrition. Accessed May 2026.
4. Joint Formulary Committee. British National Formulary (BNF). Folic acid. BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk. Accessed May 2026.
5. Medicines and Healthcare products Regulatory Agency (MHRA). Yellow Card — report a side effect. https://yellowcard.mhra.gov.uk. Accessed May 2026.

Folic Acid Products

The table below compares the two folic acid products in the Vitamins range. Both provide folic acid (vitamin B9) but differ in dose, classification, and licensed indication.

Important: This comparison is for general information only and does not replace medical advice. A prescriber will decide which treatment is suitable for you following an online consultation.