A cough that won’t go away. A persistent bloated feeling. Unexplained weight loss.

Each of these could be the result of something harmless — a cold, that burrito-forward diet you’ve been eating, a dramatically effective workout regimen. But each also could be your body’s early-warning signal for something else: cancer.

Dr. Michael Nichols, a radiation oncologist at the Novant Health Cancer Institute in Wilmington, treats many patients whose cancers began with a simple symptom that was easily ignored. Seeing a doctor is crucial.

“Cancer gives us warning signs, and if ignored in perpetuity, we miss an opportunity to catch something early,” Nichols said. The first and most important step is getting the right screenings at the right time:

• Pap tests for women starting at age 21
• Mammograms for women starting at age 40
• Prostate-specific antigen (PSA) blood work checks for men starting at age 50
• Low-dose CT chest scans for both men and women ages 50 to 80 who have a 20-plus pack-year smoking history and are current smokers or have quit within the past 15 years
• Colonoscopies for men and women starting at age 45

But after that, pay attention to symptoms that follow what Nichols called “the three-week rule” — lasting that long without improvement — and to those that are so drastic you shouldn’t even wait three weeks.

Here are possible cancer warning signs that you should never ignore.

1. Vaginal bleeding for women four or more years past menopause.

This is a “red flag” warning sign — one that should send you straight to a doctor. “Post-menopausal vaginal bleeding should be considered cancer until proven otherwise,” Nichols said. “That could be cervical or uterine cancer.” Premenopausal women who experience persistent bleeding outside their typical cycle also should get that checked out, he said.

2. A hoarse or scratchy voice that doesn’t improve.

“That hoarseness can be thyroid cancer,” Nichols said. Thyroid cancer is one of the fastest-growing cancers worldwide and women are nearly three times as likely as men to get it.

3. A lump above your collarbone.

Most women know that lumps or skin changes in the breast area need a doctor’s visit right away, but a lump above the collarbone is also concerning, Nichols said, because it could be a sign of breast cancer or lymphoma.

4. Bloating that doesn’t go away.

For women, if it’s not associated with a meal or an oncoming period, bloating could be a warning signal for ovarian cancer, Nichols said. For everyone, persistent bloating also can be a sign of gastrointestinal or pancreatic cancer.

5. Persistent rectal bleeding, even if you’re sure it’s hemorrhoids.

“I’ll very consistently hear of a colon cancer that presented with rectal bleeding and the person will say, ‘I thought it was a hemorrhoid,’” Nichols said. “If it’s persistent bleeding, I would not self-diagnose. Bright red blood is usually a hemorrhoid, but when it’s not, it’s a problem.”

6. Weight loss.

It’s extremely common for cancer to cause weight loss. When Nichols’ patients tell him they’ve lost weight, “it’s always coupled with ‘but I’m trying to lose weight,’” he said. But it’s rare for a diet or exercise plan that wasn’t causing significant weight loss before to suddenly do so, he said. “If you’ve lost 5% or more of your body weight without a very, very clear explanation, such as sickness or a drastic change to lifestyle, that should be investigated,” Nichols said. “Weight loss is a big flashing red light.”

7. A new persistent cough or coughing up blood.

“The most common cause of coughing up blood is bronchitis, but it is also a sign of lung cancer. A persistent cough should be investigated,” Nichols said. “For a lot of my lung cancer patients that is the No. 1 complaint.”

8. Ear pain.

This can be a sign of a head or neck cancer, Nichols said. Other easily missed signs: Painful swallowing or a mouth sore that won’t heal.

9. Pain during sex.

For women, persistent pain during intercourse, or bleeding after, needs a doctor’s attention, Nichols said, as it can be a sign of cervical cancer.

10. Skin changes.

Lesions that won’t heal need a doctor’s eye, Nichols said. The same is true of new or changing moles, especially those that have more than one color, are asymmetrical or have jagged borders. Melanomas can be tiny.

11. Bone pain that won’t quit.

“The key with cancer-related bone pain is it is usually relentless,” Nichols said. “It hurts whether exercising or not exercising. It hurts night or day. It might go up but doesn’t really go away.”

12. Changes in stool.

Colorectal cancers are becoming more common in younger patients, so never, regardless of your age, dismiss bowel habit changes, Nichols warned. Stool may be pencil-thin if a tumor is obstructing its passage. Feeling like you need to “go” when nothing comes out, or alternating between diarrhea and constipation are causes for further investigation.

When to see a doctor about possible cancer symptoms.

It’s easy to talk yourself out of an appointment with a primary care doctor or other physician, but when your body speaks, you should listen.

“Go with your gut,” Nichols said. “Don’t dismiss something new that’s not going away or getting worse by rationalizing it away.”

And if the sign turns out to be nothing? That’s great, Nichols said — and there’s no reason to feel the doctor’s visit was a mistake. “Patients should always feel comfortable asking their doctor about a concern,” he said. “That’s why we are here.”