Why your pill changed color

Researchers at Brigham and Women's Hospital and Harvard Medical School went through insurance claims for patients taking antiepileptic drugs and counted how many different-looking pills they had been handed. The answer was 37 colors and four shapes. A change in pill color was associated with 27 percent higher odds that a patient stopped refilling, the team reported in JAMA Internal Medicine in 2013¹.

The active ingredient and strength were the same. The pharmacy had filled the prescription with a version from a different manufacturer, which is routine in the generic market. Each maker designs its own tablet, and FDA lets them look different.

A change in appearance is still worth checking, and public tools make it possible to do that in a few minutes.

Why two versions of one generic look different

A generic has to match the brand on active ingredient, strength, dosage form and how it performs in the body. Appearance is a separate matter. "FDA generally allows minor differences in appearance between generic and brand drugs, such as in color," and "these minor differences do not affect how the medicine works," the agency's consumer Q&A says⁸. Small, allowable differences in inactive ingredients such as dyes, coatings and fillers are part of the reason, as our guide to what's actually different between generic and brand explains.

If five companies make the same generic, five different looks can sit on pharmacy shelves at once. Color is the most common difference, but shape, size, scoring and the printed code usually differ too. All of those versions can carry the same AB rating in FDA's Orange Book.

FDA does set expectations on size. In guidance finalized in October 2022⁵, it recommends that when the brand tablet is under 17 mm in its largest dimension, a generic be no more than 20 percent larger in any single dimension and no more than 40 percent larger by volume. The guidance document⁶ also says the largest dimension of a tablet should not exceed 22 mm and capsules should not exceed a standard size 00. It says nothing requiring generics to match the brand's color.

Why the pharmacy changed suppliers

Pharmacies buy generics through wholesalers and purchasing contracts, and the supplier for a given drug can change from one order to the next. A new contract, a price change, a shortage at one manufacturer, a recall or a discontinued product can all trigger a switch. State substitution laws generally let the pharmacist dispense any version FDA rates as therapeutically equivalent, so the prescription doesn't need to be rewritten when the supplier changes.

For a common drug the choice of suppliers can be wide. GxRadar's drug pages show how many generic applications FDA has approved for each of 47 common medicines, and people who take the same drug for years may see several different-looking versions over that time.

The imprint code identifies the tablet

Federal regulation requires most solid oral drugs to carry a code, a rule traced in more detail in Pill imprint codes and the 1993 rule behind them. Under 21 CFR 206.10³, a tablet or capsule may not be shipped in interstate commerce unless it is marked with an imprint that, "in conjunction with the product's size, shape, and color, permits the unique identification of the drug product and the manufacturer or distributor of the product." Identification means the active ingredients and the dosage strength. The rule encourages a letter or number "as a more effective means of identification than a symbol or logo by itself."

FDA published the rule in September 1993 and gave industry two years to retool, so it took effect on Sept. 13, 1995, according to a 1995 Federal Register clarification⁴. A small set of products are exempt.

Because of that rule, two pills that look nothing alike can be confirmed as the same drug and strength by checking each code against its official listing:

Checking a pill against its official listing

Start with the pharmacy label. It names the drug and strength, and many labels also show the National Drug Code or the manufacturer of the product dispensed. Our guide to reading a prescription label shows where to find them.

Next, look up the product in DailyMed⁹, the National Library of Medicine's database of FDA-submitted labeling. Each product's label page includes a Product Characteristics table listing color, score, shape, size in millimeters and imprint code. If you know which manufacturer's product you were given, you can compare the tablet in your hand with that listing.

Older tools are gone. NLM retired Pillbox, a federal pill identifier that let users search by imprint, color and shape, on Jan. 29, 2021. Its final data files "should not be used for pill identification," and MedlinePlus and DailyMed "do not provide pill identification," NLM's technical bulletin said⁷. DailyMed works best for confirming a pill you already have a name for.

The fastest check is the pharmacist. The pharmacy's dispensing record shows exactly which product went into your bottle, and the pharmacist can match the imprint in seconds.

What research says about appearance and adherence

Two widely cited studies from the same Boston research group looked at what happens after a pill's appearance changes:

Both studies measured nonpersistence, meaning a patient failed to refill on time, rather than health outcomes. The 2014 paper listed among its limitations that "clinical outcomes were not addressed," and found that statins had the most appearance changes and beta-blockers the fewest, according to its abstract². The 2013 authors argued that their findings support "a reconsideration of current regulatory policy that permits wide variation in the appearance of bioequivalent drugs," their abstract said. Statins such as atorvastatin and ACE inhibitors such as lisinopril belong to the drug classes in that heart study.

The likely mechanism is ordinary confusion. A patient who sees an unfamiliar tablet may suspect an error and set the bottle aside until someone explains it.

When to call the pharmacy

An unexplained change in appearance is a good reason to call. Pharmacists field this question constantly, and dispensing errors, while uncommon, do happen. Call if the imprint on the new tablets does not match what the label or DailyMed lists, if tablets in one bottle look different from each other, or if the strength on the label differs from what your prescriber told you.

Caregivers who sort pills into weekly organizers have a particular reason to keep the pharmacy's description handy, since tablets lose their bottle once they are sorted. Writing down each medicine's imprint code makes later checks quick. Any question about whether a new version is right for you, or about side effects after a switch, belongs with your pharmacist or prescriber.