Yes, pills can get moldy. Tablets, capsules, and other solid medications contain ingredients like starch, lactose, and plant-based compounds that serve as food sources for mold when moisture is present. While it’s not common under proper storage conditions, mold contamination of pharmaceuticals is a documented problem that has led to FDA recalls, serious illness, and in rare cases, death.
What Makes Pills Vulnerable to Mold
Mold needs two things to colonize a surface: moisture and something to eat. Most pills deliver both. A typical tablet contains not just the active drug but fillers and binders like corn starch, lactose, magnesium stearate, and povidone. These organic materials give fungi a foothold once humidity enters the equation. Herbal medications with high lipid and polysaccharide content are especially prone to fungal contamination.
During manufacturing, tablets are typically dried to a water content of around 3%, which makes them inhospitable to mold. But that protection erodes over time if pills are stored in humid environments. Aspergillus species, one of the most common indoor molds, thrive under high humidity. One documented case of pharmaceutical contamination occurred when a product was stored in hot, humid conditions (above 86°F and 75% relative humidity) for more than six months.
How to Spot Mold on Medication
Mold on pills can look very different depending on the species involved. It may appear as a fuzzy, cottony, or granular coating, or as a smooth, velvety film. Colors range widely: white, gray, green, black, yellow, brown, or even colorless. Any visible discoloration or unusual texture on a pill’s surface is a red flag.
Your nose may catch the problem before your eyes do. Mold releases volatile organic compounds that produce a distinctive musty smell. If you open a pill bottle and notice an off or musty odor, that alone is reason to suspect contamination, even if you can’t see anything unusual. Changes in the pill’s texture, such as softness, crumbling, or a sticky surface, can also signal moisture damage that precedes or accompanies mold growth.
Health Risks of Moldy Pills
Swallowing a mold-contaminated pill isn’t the same as eating a piece of bread with a spot of mold on it. Some molds produce mycotoxins, toxic substances that can cause both sudden and long-term illness. Ingesting a large amount at once typically causes gastrointestinal symptoms: abdominal pain, nausea, vomiting, and diarrhea. Other acute symptoms include headache, dizziness, blurred vision, and fever.
Chronic low-level exposure to mycotoxins is potentially more dangerous. Over time, it can impair cognitive function, increase asthma risk, and raise cancer risk. In the most extreme documented cases, contaminated pharmaceuticals have been fatal. In 2013, steroid injections contaminated with fungal species at a compounding center in Boston caused fungal meningitis that killed 55 patients. In a separate incident, five immunosuppressed patients died of intestinal fungal infection traced to contaminated allopurinol tablets.
These extreme cases involved injectable drugs or patients with severely weakened immune systems. For a healthy person who accidentally swallows a slightly moldy tablet, the risk is far lower, but there’s no way to know which mold species or mycotoxins are present without laboratory testing. The safe move is to discard any medication you suspect is contaminated.
Mold Also Degrades the Drug Itself
Beyond the direct toxicity of mold, fungal growth can break down the active ingredient in a medication, making it less effective or entirely useless. The FDA has documented that microbial contamination leads to drug degradation and subpotency. Between 2014 and 2017, there were 197 adverse event reports tied to microbial or fungal contamination of pharmaceuticals, with 32 of those documenting serious outcomes.
A familiar example: when aspirin absorbs too much moisture, it breaks down into vinegar (acetic acid) and salicylic acid. You might notice a vinegar-like smell when you open the bottle. If you take those degraded tablets, they can cause stomach distress and won’t deliver the intended dose. The same principle applies to many other medications. A pill that looks or smells wrong may no longer contain enough active drug to work.
Where You Store Pills Matters More Than You Think
The medicine cabinet in your bathroom is one of the worst places to keep medication, despite being the most traditional spot. Research measuring actual conditions in US homes found bathroom humidity ranging from 33% to 100% relative humidity, with temperatures swinging from about 57°F to nearly 89°F. Hot showers send humidity soaring well past the safety threshold for moisture-sensitive drugs.
Pharmaceutical standards define a “dry place” as one averaging no more than 40% relative humidity at 68°F. Controlled room temperature for medications is 68°F to 77°F, with brief excursions up to 86°F considered acceptable. Bathrooms and kitchens regularly exceed both limits. In one study, almost a quarter of medications in US households had a moisture or humidity issue based on where they were stored.
The best storage location is a bedroom closet, a hallway cabinet, or another cool, dry area away from steam, cooking heat, and direct sunlight. Keep pills in their original containers with the lids tightly closed. Those containers are designed and tested to limit moisture penetration. Transferring pills to decorative boxes or leaving bottles open invites the exact humidity exposure that promotes mold.
When to Toss Your Medications
Check your pill bottles periodically, especially if you live in a humid climate or store medications long-term. Discard any pills that show visible discoloration, unusual spots, a fuzzy or filmy coating, a musty or vinegar-like smell, or a change in texture like softness or crumbling. Expired medications stored in less-than-ideal conditions deserve extra scrutiny, since protective coatings and container seals degrade over time.
If you’ve been storing pills in a bathroom or kitchen for months, inspect them closely even if they look fine at first glance. Mold can start as colorless growth that’s easy to miss. A pill that dissolves differently on your tongue, tastes off, or crumbles when it shouldn’t is telling you something has changed at the chemical level, whether from mold, moisture, or both.