Common Causes (Ranked by Likelihood)
B vitamins are water-soluble, meaning the body excretes any excess in urine. High doses of B6 (pyridoxine), B12 (cobalamin), and riboflavin (B2) produce a distinctly chemical, medicinal, or plastic-like urine smell when excreted. Many multivitamins contain 100-2000% of the daily value for B vitamins — all of that excess goes directly into urine. B2 (riboflavin) also makes urine bright yellow-orange. The chemical smell is from the vitamin compounds themselves and their metabolites. It's harmless.
Many medications produce distinctive urine odors as they're metabolized and excreted. Antibiotics (particularly penicillin, amoxicillin, and sulfonamides) are well-known for causing chemical, plastic, or medicinal urine smells. Metformin (diabetes medication) causes a metallic or chemical smell. Diuretics change urine concentration and composition. Asparagus, which most people know for its distinctive sulfurous urine smell, can in some people produce a more chemical note depending on their metabolism. Various herbal supplements (elderberry, echinacea, fenugreek) also affect urine odor.
When dehydrated, urine becomes highly concentrated — the same metabolic waste compounds are present in a much smaller volume of fluid, intensifying any unusual odors including plastic or chemical notes. The compounds responsible for the plastic smell (often from normal metabolic processes or dietary sources) are always present at low levels but only become noticeable when urine is concentrated. Dark yellow or amber urine alongside the unusual smell suggests dehydration.
Most UTIs produce a foul or ammonia-like smell, but certain bacterial species produce different volatile compounds. Proteus mirabilis produces urease that generates ammonia and other compounds that some describe as chemical or plastic-like. Klebsiella and Pseudomonas infections can produce more distinctive, chemical-adjacent urine odors than typical E. coli UTIs. If the plastic smell is accompanied by burning, frequency, or urgency, a UTI should be ruled out.
Phenylketonuria (PKU) is a rare metabolic disorder where the body can't metabolize phenylalanine, causing it to accumulate and be converted to phenylpyruvate, which is excreted in urine and produces a musty or chemical/plastic smell. PKU is screened for at birth in all US newborns (newborn metabolic screen) and is almost always diagnosed in infancy. Adults with undiagnosed or untreated PKU would have significant neurological symptoms alongside the unusual urine smell. The musty/plastic urine smell is listed as a classic PKU symptom, though the modern screening program means it's rarely an undiagnosed adult condition.
How to Fix It
Adjust Vitamins and Supplements
$0The simplest intervention when vitamins are the cause.
- 1Skip your multivitamin for 2-3 days and see if the plastic smell disappears — this confirms vitamins as the cause.
- 2If confirmed, switch to a multivitamin with lower doses of B vitamins (look for 100% DV rather than 500-2000% DV).
- 3Take vitamins with food rather than on an empty stomach — slows absorption and reduces the concentration spike in urine.
- 4Consider splitting doses — taking half in the morning and half at night distributes the excretion load.
- 5B vitamins are water-soluble and safe, so the smell is cosmetic rather than a health concern.
Improve Hydration
$0Dilutes concentrated compounds causing the odor.
- 1Drink enough water that urine is pale yellow by midday — most adults need 2-3 liters daily.
- 2The first morning urine will always be most concentrated and most odorous — this is normal.
- 3If the plastic smell persists even with well-hydrated, pale-yellow urine, hydration alone isn't the cause.
- 4Spread water intake throughout the day rather than drinking large amounts at once.
- 5Reduce caffeine and alcohol, which are diuretics that concentrate urine.
Rule Out UTI
$10-100If any urinary symptoms accompany the unusual smell.
- 1Use a home UTI test strip (available at pharmacies, $10-15 for 3 strips) to check for nitrites and leukocyte esterase — these indicate bacterial infection.
- 2See a doctor if home test is positive or if you have burning, frequency, urgency, or pain alongside the smell.
- 3UTIs are confirmed with a urine culture and treated with antibiotics (3-7 day course).
- 4Don't delay UTI treatment — untreated UTIs can progress to kidney infections.
- 5After antibiotic treatment, the unusual smell should resolve along with other UTI symptoms.
When to Call a Professional
Plastic or chemical smell with burning, frequency, or urgency — test for UTI and see a doctor if positive.
Smell with lower back or flank pain and fever — possible kidney infection; go to urgent care.
Smell in a child not taking vitamins with developmental concerns — rare metabolic condition; consult pediatrician.
Persistent plastic smell for more than 2 weeks not explained by vitamins or diet — see a doctor for urinalysis and metabolic screening.
How to Prevent It
Choose multivitamins with 100% DV rather than mega-dose versions — excess B vitamins all go to urine.
Take vitamins with food to slow absorption and reduce urinary concentration spikes.
Stay well hydrated — dilutes all urinary compounds, reducing odor intensity.
Keep track of when urine odor changes correlate with new supplements or medications — this makes cause identification straightforward.
Complete UTI courses of antibiotics fully — incomplete treatment leads to recurrent infections.
Why B Vitamins Make Urine Smell Chemical
B vitamins — particularly riboflavin (B2), pyridoxine (B6), and cyanocobalamin (B12) — are among the most common causes of unusual urine odor because they're water-soluble and the body can't store excess amounts. Any B vitamin intake above current needs is filtered by the kidneys and excreted in urine, sometimes within hours of taking a supplement. The chemical/plastic smell comes from the vitamin compounds themselves and their metabolic breakdown products.
Riboflavin (B2) is particularly notable: it's bright yellow-orange in pure form, which is why B vitamin supplements turn urine a vivid yellow. The concentration of riboflavin and its fluorescent metabolites in urine produces both the color and a chemical smell. Pyridoxine (B6) metabolites also contribute to a medicinal or chemical odor. High-dose B vitamin supplements (common in energy drinks and many multivitamins) can produce a very pronounced effect.
This is entirely harmless — the vitamins are doing exactly what they're supposed to (water-soluble vitamins are excreted when excess). But if the smell is bothersome, switching to a lower-dose multivitamin or food-based B vitamins (which are better absorbed and produce less urinary excess) usually resolves it.
Frequently Asked Questions
B vitamins (B2, B6, B12) are water-soluble, so excess amounts are excreted directly in urine. High-dose multivitamins contain 500-2000% of the daily value for B vitamins — your body uses what it needs and the rest goes to urine, producing a chemical or plastic smell. It's harmless. Try a lower-dose multivitamin or skip a few days to confirm vitamins are the cause.
UTI urine typically smells foul, ammonia-like, or strongly unpleasant. Vitamin-related urine smell is more chemical, medicinal, or plastic-like — distinctive but not as offensive as UTI smell. The key differentiator is other symptoms: UTI comes with burning, urgency, or frequency. Vitamin smell appears without any urinary discomfort.
Yes — many energy drinks contain very high doses of B vitamins (1000%+ DV of B12, B6) and other compounds that produce noticeable urine odor changes. The chemical smell after drinking energy drinks is a well-documented and harmless effect of the B vitamin overload. It typically appears within 1-2 hours and resolves within 8-12 hours.
In most cases, no — it's a harmless side effect of vitamins, supplements, or medications. The exceptions are: plastic smell with UTI symptoms (needs antibiotic treatment), severe smell with other health changes (warrants medical evaluation), and in rare cases, the smell could indicate a metabolic condition. But the overwhelming majority of people with plastic-smelling urine are just excreting excess B vitamins.