Swollen Lymph Nodes: When Should You Worry?

The short answer: most swollen lymph nodes come from infection, and the node may take several weeks to shrink back down. In primary care, only about 1.1% of unexplained cases turn out to be cancer. Worry more about a node above the collarbone, a node that feels hard or fixed in place, a node larger than 1 cm that persists past 4 weeks, or swelling that comes with fever, drenching night sweats, or unexplained weight loss. Any of those features deserves a doctor visit.

What counts as a swollen lymph node?

Lymph nodes are small filters for the immune system, clustered in the neck, armpits, and groin. Doctors generally consider a node abnormal when it grows larger than 1 cm, about 0.4 inch (Gaddey & Riegel, American Family Physician 2016). The threshold shifts by location. Epitrochlear nodes, near the inner elbow, are abnormal above 5 mm. Inguinal nodes in the groin can measure up to 2 cm in healthy adults and still be normal.

Location matters as much as size. Supraclavicular nodes, just above the collarbone, should not be palpable at all, and the same goes for popliteal (behind the knee) and iliac nodes (AFP 2016). A node you can feel in one of those spots warrants evaluation even when it is small.

What usually causes swollen lymph nodes?

Infections are the most common cause, according to the NIH's MedlinePlus. Colds, flu, ear infections, tonsillitis, and skin infections all recruit nearby nodes. In children, self-limiting viral illnesses are the most common cause of swollen neck nodes (AFP 2016).

Infectious mononucleosis deserves its own mention. It is common among teenagers and young adults, it swells the glands in the neck and armpits, and most people recover in two to four weeks, though fatigue can drag on longer (MedlinePlus). Less common causes include autoimmune conditions such as lupus, HIV, and medications. American Family Physician lists allopurinol, atenolol, captopril, carbamazepine, phenytoin, penicillins, and trimethoprim/sulfamethoxazole among the drugs that can enlarge nodes (AFP 2016). A neck node that persists for months can also come from atypical mycobacteria, cat-scratch disease, or sarcoidosis.

One reassuring detail: the soreness of an infection-related node usually fades within a couple of days, but the node itself "may not return to its normal size for several weeks" (MedlinePlus). A node that is slowly deflating after a cold is behaving normally.

How often are swollen lymph nodes cancer?

Rarely. Among patients who see a primary care doctor for unexplained lymphadenopathy, only about 1.1% of cases are related to malignancy (AFP 2016). Age changes the math: cancer is found in 0.4% of patients younger than 40 and about 4% of patients 40 and older.

Location changes it more. In studies of patients 40 and older with supraclavicular lymphadenopathy, 34% to 50% had a malignancy (AFP 2016). That is why a node above the collarbone is treated differently from one under the jaw. Duration cuts both ways: swelling that has lasted less than two weeks, or more than 12 months without growing, is unlikely to be neoplastic. The uncomfortable middle, a node persisting and growing over four to six weeks, is what prompts a workup.

Which features are red flags?

Doctors weigh how a node feels and what comes with it. See a doctor promptly for any of the following:

• A node above the collarbone (supraclavicular), at any size.
• A node that feels hard, irregular, or fixed in place rather than soft and mobile (MedlinePlus).
• A painless node that keeps growing. The National Cancer Institute lists "painless, swollen lymph nodes in the neck, underarm, or groin" as a presenting sign of Hodgkin lymphoma (NCI).
• Fever for no known reason, drenching night sweats, or unexplained weight loss in the past 6 months (NCI). We cover the first two in our guide to night sweats and the last in our guide to unintentional weight loss.
• A node larger than 1 cm with no infection to explain it, or one still enlarged after about four weeks.
• Red, tender skin over the node, which can signal a bacterial infection of the node itself that needs treatment.

Age above 40 and male sex also raise the statistical risk of a serious cause (AFP 2016), so the same node earns a faster workup in a 60-year-old than in a teenager.

What if nodes are swollen in more than one area?

Doctors call this generalized lymphadenopathy, defined as enlargement of more than two noncontiguous lymph node groups, and it usually points to a systemic process (AFP 2016). Causes include acute HIV infection, mononucleosis and other viral illnesses, mycobacterial infection, lupus, and medication reactions. This pattern is not a do-it-yourself diagnosis. It calls for a doctor visit and usually blood work, including HIV testing when risk factors are present.

When should you see a doctor?

Use the cause-and-clock test. If a node swelled during an obvious infection, is tender, and is trending smaller, you can watch it; expect several weeks for full shrinkage (MedlinePlus). Book a visit if the node is still enlarged after about four weeks, is growing, or was never linked to an infection at all. Book it this week if any red flag from the list above is present: supraclavicular location, hard or fixed texture, painless growth, fevers, drenching night sweats, or weight loss.

In children, MedlinePlus advises contacting a provider for any node wider than 1 centimeter. Our red flags guide covers warning signs that should never wait, and our post on when to see a doctor gives thresholds for other symptoms.

What will the doctor do?

The history and physical exam identify the cause most of the time. The doctor will map which node groups are involved, measure the nodes, check texture and mobility, review your medications, and ask about exposures: sick contacts, cats, travel, and sexual history. For localized swelling with no red flags, guidance supports observing for four weeks before escalating (AFP 2016).

If the node persists or red flags exist, the next steps are blood tests aimed at the likely causes and, when needed, sampling the node. Fine-needle aspiration has a reported sensitivity of 85% to 95% and specificity of 98% to 100% for detecting malignancy, with overall diagnostic accuracy approaching 90% (AFP 2016). Some patients go straight to an excisional biopsy, where the whole node is removed, because certain diagnoses such as lymphoma require the node's full architecture. Neck nodes are often evaluated by an ENT specialist, since the head and neck drain through them.

The bottom line

Feel the node, note the date, and think about what else is going on. A tender node during a cold that shrinks over a few weeks is your immune system working. A node over 1 cm that persists past four weeks, any palpable node above the collarbone, a hard or fixed node, or swelling paired with fevers, drenching night sweats, or unexplained weight loss needs a doctor. The odds are on your side: about 1.1% of unexplained cases in primary care are cancer. But the exceptions are exactly the ones a short exam, basic labs, and, if needed, a needle sample are good at finding.

Last updated: September 2026. This article is for informational purposes only and does not constitute medical advice. It cannot diagnose your symptoms. Seek prompt care for a rapidly enlarging or very painful node, difficulty breathing or swallowing, or high fever, and do not stop or change a prescribed medication without speaking to the prescriber.