Vitamin B2 (Riboflavin-5-Phosphate)

Active coenzyme form of vitamin B2 that doesn't require conversion, offering superior bioavailability

Scientific nameRiboflavin-5-Phosphate FormulaC17H21N4O9P Molecular weight456.34 g/mol CAS146-17-8

90 absorption score

9 safety / 10

35 USD per month

5 documented interactions

Check it against something

Evidence level A

Vitamin B2 (Riboflavin-5-Phosphate) with:

90 out of 100

Works better together Take together — same timing window amplifies the synergy.

Check it against your whole stack →

What it does

mechanism and evidence for each claim

Superior bioavailability

Better absorbed and utilized than regular riboflavin

Active form bypasses conversion requirements Evidence B-grade Immediate

Enhanced energy metabolism

Direct participation in cellular energy production

Immediate availability as FMN coenzyme Evidence A-grade 1-2 weeks

Optimal for conversion-impaired individuals

Ideal for those with poor riboflavin phosphorylation

Bypasses riboflavin kinase enzyme requirement Evidence B-grade 1-2 weeks

Enhanced antioxidant support

More effective glutathione reductase support

Direct FMN availability for antioxidant enzymes Evidence B-grade 2-4 weeks

Migraine prevention efficacy

May be more effective than riboflavin for migraines

Better mitochondrial energy support in brain Evidence C-grade 8-12 weeks

Others take these for the same thing

Same goal, different mechanism — check any of them against this one

Turmeric Anti-inflammatory & antioxidant 300-1000mg A 3% Ashwagandha Stress management & energy 300-600mg A 75% Vitamin B12 (Cyanocobalamin) Energy & nerve support 250-1000 mcg A 70% Coenzyme Q10 (CoQ10) Heart health & cellular energy 100-200mg A 10% Phosphorus Bone health & energy metabolism 700-1250mg A 80% Vitamin B3 (Niacinamide) Energy & skin health (no flush) 100-1000 mg A 88%

Every pair we checked

12 combinations scored by the engine

Vitamin B2 (Riboflavin-5-Phosphate) + Caffeine No documented interaction either way No known interaction 70

Vitamin B2 (Riboflavin-5-Phosphate) + Creatine Monohydrate No documented interaction either way No known interaction 70

Vitamin B2 (Riboflavin-5-Phosphate) + Whey Protein No documented interaction either way No known interaction 70

Vitamin B2 (Riboflavin-5-Phosphate) + Turmeric No documented interaction either way No known interaction 70

Vitamin B2 (Riboflavin-5-Phosphate) + Lactase Improved calcium absorption when consuming dairy Works better together 82

Vitamin B2 (Riboflavin-5-Phosphate) + Bovine Collagen Essential for collagen synthesis and cross-linking Works better together 82

Vitamin B2 (Riboflavin-5-Phosphate) + DHA Prevents oxidation of DHA and enhances stability Works better together 82

Vitamin B2 (Riboflavin-5-Phosphate) + Vitamin D3 R5P may enhance B6 activation Works better together 86

Vitamin B2 (Riboflavin-5-Phosphate) + Fish Oil (EPA/DHA) Protects fish oil from oxidation Works better together 90

Vitamin B2 (Riboflavin-5-Phosphate) + Magnesium Oxide Required for FMN-dependent enzyme function Works better together 94

Vitamin B2 (Riboflavin-5-Phosphate) + Calcium Carbonate Essential for calcium absorption and utilization Works better together 94

Vitamin B2 (Riboflavin-5-Phosphate) + Vitamin B3 (Niacinamide) Both work together in energy metabolism Works better together 98

Dosage

Morning with food

Daily10-50 mg

Maintenance5-25 mg

Therapeutic25-100 mg

Migraine prevention100-200 mg

MaximumNo established upper limit

Before you take it

VeganYes

When to expect it

First EffectsImmediate availability as coenzyme

Peak Benefits4-8 weeks for energy and antioxidant benefits

Deficiency Development1-2 months with inadequate B2 intake

Toxicity OnsetNo known toxicity from oral intake

How to measure it

$60-100

MarkerErythrocyte glutathione reductase activity (EGRAC)

OptimalActivity coefficient <1.2

FrequencyOnly if monitoring therapeutic dosing or deficiency

What people actually reported to the FDA

CAERS, 5 reports naming it as the suspect

Most reported effects

Chromaturia 2

Autism 1

Mitochondrial dna mutation 1

Alanine aminotransferase increased 1

Aspartate aminotransferase increased 1

Named as the suspect 5 reports of 23 that mention it at all

Serious outcome 75% hospitalisation, emergency room or worse

Other Serious or Important Medical Event3

Other Outcome1

Hospitalization1

Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →

What actually reaches you

The label counts the carrier, your body does not

Absorption Very high 90 of 100 · best absorbed form of this compound

Delivered daily 27 mg

Cost per 100 mg delivered $4.32 comparative — uses the absorption score, not a measured percentage

Works better with

3 documented

Niacin B3

Both work together in energy metabolism

Complementary roles in electron transport · level A

Vitamin B6

R5P may enhance B6 activation

Both involved in amino acid metabolism · level B

Magnesium

Required for FMN-dependent enzyme function

Cofactor for riboflavin-dependent enzymes · level A

What not to take with Vitamin B2 (Riboflavin-5-Phosphate)

2 documented

Alcohol

Reduces riboflavin status and enzyme function

Interferes with riboflavin metabolism and storage · moderate significance

Light Exposure

R5P may be more stable but still light-sensitive

Photodegradation of the phosphate form · moderate for storage significance

Medication interactions

Discuss these with a pharmacist before combining

tricyclic-antidepressants Minor

May reduce riboflavin levels

What to do: R5P may be beneficial due to better absorption

phenothiazines Minor

May increase riboflavin requirements

What to do: R5P form may overcome interaction

Available forms

bioavailability compared

Riboflavin-5-Phosphate (R5P) 90

Riboflavin-5-Phosphate (R5P): Active form, No conversion needed, Superior absorption, Better for impaired metabolism

Food sources

before you supplement

R5P is not found naturally in foods Only available as supplement · 90

Too little

deficiency signs

Same as riboflavin deficiency:
Cracked lips and mouth corners
Sore throat and swollen tongue
Eye irritation and light sensitivity
Skin disorders and dermatitis
Fatigue and weakness
Anemia

Too much

toxicity signs

No known toxicity from oral intake
Bright yellow urine (harmless)
No upper limit established
Excess excreted in urine
Same safety profile as riboflavin

Who benefits most

conversion-impaired-individuals

Bypasses riboflavin kinase enzyme requirement

10-50 mg daily

severe-migraine-sufferers

May be more effective than regular riboflavin

25-100 mg daily

therapeutic-protocols

Maximum bioavailability for clinical applications

25-200 mg daily

malabsorption-disorders

Better absorption in compromised digestive systems

25-100 mg daily

optimization-focused

Want maximum B2 efficacy regardless of cost

10-50 mg daily

Where to buy it

compare forms first

Look for Vitamin B2 (Riboflavin-5-Phosphate) at 10-50 mg per serving. The form that matters here is Riboflavin-5-Phosphate (R5P).

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What else affects it

Beyond other supplements

Alcohol

Reduces riboflavin status and enzyme function

Interferes with riboflavin metabolism and storage

How it works

Direct availability as FMN (flavin mononucleotide) coenzyme
Bypasses riboflavin kinase phosphorylation step
Immediately functional in electron transport chain
Direct cofactor for glutathione reductase
Enhanced cellular uptake compared to riboflavin
More efficient tissue distribution

Key findings

what the evidence supports

Superior bioavailability compared to riboflavin (limited studies)
Better for individuals with conversion impairments
Enhanced antioxidant enzyme support
Limited but promising research on enhanced efficacy

Sources: NIH Examine.com · data reviewed 2026-08-02

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Vitamin B2 (Riboflavin-5-Phosphate)?

Documented effects: Superior bioavailability; Enhanced energy metabolism; Optimal for conversion-impaired individuals; Enhanced antioxidant support. Better absorbed and utilized than regular riboflavin

How much Vitamin B2 (Riboflavin-5-Phosphate) should you take per day?

The common daily range is 10-50 mg. By goal — maintenance: 5-25 mg; therapeutic: 25-100 mg; migraine prevention: 100-200 mg; maximum: No established upper limit.

When is the best time to take Vitamin B2 (Riboflavin-5-Phosphate)?

Morning with food. First effects are typically reported within Immediate availability as coenzyme.

What are the side effects of Vitamin B2 (Riboflavin-5-Phosphate)?

At excessive doses: No known toxicity from oral intake, Bright yellow urine (harmless), No upper limit established, Excess excreted in urine, Same safety profile as riboflavin. Safety rating at normal doses is 9 out of 10.

What should you not take with Vitamin B2 (Riboflavin-5-Phosphate)?

Separate it from Alcohol, Light Exposure by two to four hours. Reduces riboflavin status and enzyme function

Does Vitamin B2 (Riboflavin-5-Phosphate) interact with medications?

Documented interactions with tricyclic-antidepressants, phenothiazines. Discuss these with a pharmacist before combining.

How do you know if you need Vitamin B2 (Riboflavin-5-Phosphate)?

The marker is Erythrocyte glutathione reductase activity (EGRAC), optimal range Activity coefficient <1.2. Common deficiency signs: Same as riboflavin deficiency:, Cracked lips and mouth corners, Sore throat and swollen tongue, Eye irritation and light sensitivity.

Taken for

62 Energy & Metabolism

Vitamin B12 (Methylcobalamin) · Ashwagandha · Vitamin B12 (Cyanocobalamin)

49 Liver & Detox

Turmeric · Vitamin C (Ascorbic Acid) · D-Mannose