What’s a ‘black box’ warning? A pharmacologist explains how these labels protect patients
On November 10, 2025, the FDA made headlines by announcing the removal of the black box warning from hormone replacement therapy (HRT) for menopause, a significant shift that reflects evolving understandings of the therapy’s safety profile. Black box warnings, officially termed boxed warnings, serve as critical alerts to healthcare professionals regarding potential serious risks associated with specific medications. These warnings, which are prominently displayed within a black box on product packaging, are intended to ensure that clinicians are aware of the most severe adverse effects a drug may cause, thus influencing their prescribing decisions. The history of black box warnings dates back to the Fair Packaging and Labeling Act of 1966, which mandated that drug manufacturers provide comprehensive information about their products, including potential health risks.
The FDA’s decision to lift the warning from HRT follows years of re-evaluation of the therapy’s risks and benefits. Originally issued in 2003, the warning was prompted by findings from the Women’s Health Initiative, which indicated an increased risk of breast cancer among women using HRT without a corresponding reduction in heart disease risk. However, subsequent analyses and new data have indicated that HRT may be safe for women aged 50 to 60, especially with the advent of newer formulations that are safer. This change not only reflects a shift in the understanding of HRT but also underscores the broader implications of black box warnings on clinical practice. For instance, while antidepressants are effective in treating depression, they carry a black box warning due to the heightened risk of suicide among young patients, which can deter clinicians from prescribing them, particularly for vulnerable populations.
Moreover, the impact of black box warnings extends beyond clinical decision-making into the legal realm. In many states, these warnings can establish a standard of care, making clinicians potentially liable if they deviate from the guidelines outlined in the product inserts. For example, the black box warning on thalidomide emphasizes the need for pregnancy precautions due to the risk of birth defects, which could lead to legal repercussions if not adhered to. As medical knowledge evolves, the FDA remains vigilant in updating these warnings, ensuring that healthcare providers have the most current information to guide their prescribing practices. The recent removal of the black box warning from HRT not only signifies a positive development in menopause management but also highlights the dynamic nature of drug safety regulations and their profound influence on patient care.
Black box warnings can influence whether or not clinicians decide to prescribe a drug.
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A “black box” warning on a health product sounds pretty scary – maybe even more so when it’s suddenly being taken off the packaging.
Americans were reminded of this type of public health messaging on Nov. 10, 2025, when the Food and Drug Administration announced it is removing the “black box” warning from
hormone replacement therapy
for menopause.
But what are these warnings, anyway? What’s their history, and how do they affect a drug’s use?
I am a
clinical pharmacologist and pharmacist
studying
drug prescribing
,
safety
and
effectiveness
for over 25 years.
Black box warnings – or as the FDA officially calls them, boxed warnings – are a tool for alerting pharmacists and clinicians that the medication may have serious risks. These health care professionals are then expected to communicate those risks to consumers.
An official source of drug information
Black box warnings for particular medications appear on the product package inserts that the FDA requires pharmaceutical companies to create for each prescription drug.
Product package inserts provide official information about the drug to health care professionals. These pamphlets are attached to bulk containers of drugs purchased by pharmacies so that the pharmacist has the most updated official information on the product. The package inserts are also published in textbooks such as the
Physician’s Desk Reference
and on websites maintained by drug manufacturers.
The requirement for product package inserts came out of a consumer protection law passed in 1966, called the
Fair Packaging and Labeling Act
, which aimed to prevent unfair or deceptive packaging in products used by consumers.
The package insert carries a
set of official information
about the drug, provided by the manufacturer and regulated by the FDA. The insert must include who the drug is approved for, proper dosing and administration, and a description of the key clinical trial results that showed it was effective and safe.
It must also disclose any health risks that the drug poses – such as a boxed warning.
Flagging safety risks
The FDA has two categories for the health risks that medications could pose:
precautions and warnings
. Both are listed on the package insert.
Precautions warn clinicians of possible harm that could result in minor or moderate injury to patients. Warnings, on the other hand, alert them to the potential risk of dangerous adverse events that could result in serious injury or death. The
most serious warnings
for a drug are called boxed warnings. The text of those warnings is enclosed by a black box on the insert so they will not be missed by clinicians.
According to a 2022 study,
more than 400 medications
currently carry black box warnings.
The FDA announced it was removing the black box warning from hormone therapy for menopause.
Antidepressants are one example. While such drugs can lessen the severity of depression symptoms, researchers have found that during the first few weeks of taking them, patients have an increased risk of suicide – particularly
children and young adults
. The FDA first
issued a black box warning
about the drugs’ use in children and adolescents in 2004 and expanded the warning to young adults in 2007.
Another example is
clozapine, a drug used to suppress delusions
experienced by people with schizophrenia. Although the drug is
very effective
, the FDA first gave it a black box warning when it was
reintroduced to the market in 1989
because it can stop the production of white blood cells, potentially leading to life-threatening infections.
Hormone replacement therapy for menopause got its black box warning in 2003 after a clinical trial called the
Women’s Health Initiative
pointed to an increased risk of breast cancer without a reduced risk of heart disease in women who used it.
In subsequent years, reanalyses of the
Women’s Health Initiative
results, as well as data from other studies, have shown that the therapy is safe in women ages 50 to 60.
Newer, safer formulations of estrogen and progestin
have also emerged. These factors
prompted the FDA to remove the warnings
in November 2025, saying the therapy
doesn’t pose significant risks
.
Medical and legal realities
Black box warnings
can influence clinicians’ choice
of whether or not to prescribe a particular drug. For example, since other drugs for schizophrenia do not carry the serious risks that clozapine does, clinicians usually reserve that medicine for people who could not use those other drugs.
The black box warnings can also
play a role in malpractice cases
. In some states, package inserts and any warnings they contain can be used to establish a standard of care, leaving clinicians who deviate from them liable for damages. In other states, the warnings they list can be used to support findings of negligence.
For instance, the black box warning on the
insert of the drug thalidomide
states it can cause birth defects. It instructs clinicians to obtain a
a negative pregnancy test before use and ensure the patient is not able to get pregnant or is taking precautions to avoid pregnancy before prescribing. Failure to do so could make the clinician liable if the person taking the drug bears a child with birth defects.
Product package inserts are living documents. As new information becomes available, the FDA may find a medication’s risk is untenable and request the drug be removed from the market. Or it may decide to remove the boxed warning from the drug if new data shows the drug is less dangerous than previously thought.
C. Michael White does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
