What does one blue fingernail mean on a man?

Quick Answers

Having one blue fingernail can indicate a few different conditions in men:

  • Bruising under the nail from injury
  • Fungal infection
  • Melanoma (skin cancer)
  • Raynaud’s phenomenon
  • Low oxygen levels

While one blue nail is usually harmless, it’s important to see a doctor to determine the underlying cause. Treatment will depend on the diagnosis.

Looking at the Possible Causes

There are a several potential reasons why a man might have a single blue fingernail:


One common and benign cause is bruising under the nail from some kind of minor injury. If the fingernail was hit or smashed in an accident, it can lead to a collection of blood under the nail. This trapped blood turns the nail blue or black and purple.

As the bruise heals over the next few weeks, the discoloration will grow out with nail growth and eventually disappear. No treatment is needed unless the injury is severe.

Fungal Infection

A fungal infection of the nail, called onychomycosis, can also turn a nail blue or black. The infection is caused by dermatophytes, yeasts or molds that get under the nail and begin growing.

As the fungus spreads, it can damage the nail bed and cause thickening, distortion, and dark discoloration of the nail. Often the nail will become brittle and start to separate from the nail bed.

This type of fungal infection is more common on toenails but can occasionally infect fingernails as well. It can be challenging to treat and may require oral antifungal medication.


While less common, a blue, black or dark brown discoloration in a nail can be a sign of melanoma, a dangerous skin cancer. Melanoma forms when pigment-producing cells called melanocytes become damaged and begin multiplying out of control.

When melanoma occurs under the nail, it can cause streaks or patches of unusual coloring as the cancerous cells increase in number. This is called subungual melanoma and it accounts for around 2-3% of all melanoma cases.

Catching melanoma early is crucial, so any nail discoloration that does not go away on its own should be evaluated by a dermatologist. They can perform a biopsy if melanoma is suspected.

Raynaud’s Phenomenon

Raynaud’s phenomenon is a condition where blood vessels in the fingers and toes temporarily constrict in response to cold temperatures or stress. This limits blood supply to the digits and can cause them to turn white, then blue, then red as the vessels reopen.

During the blue stage, the affected nails will also look pale or cyanotic. After warming up for 15-30 minutes, the normal color should return. Raynaud’s is more common in women but can occur in men too.

If episodes are severe or frequent, medication may be prescribed to help dilate the blood vessels.

Low Oxygen Levels

In some instances, a bluish fingertip or nail can signal low oxygen levels in the blood. This is referred to as peripheral cyanosis. It occurs when reduced oxygen is circulating to the extremities.

Causes include respiratory conditions such as chronic obstructive pulmonary disease (COPD), pneumonia, sleep apnea, and living at high altitudes. Heart problems like congenital heart defects or pulmonary hypertension can also lead to cyanosis.

Checking oxygen saturation levels with a pulse oximeter can help diagnose the severity. If oxygen is extremely low, supplemental oxygen may be prescribed.

When to See a Doctor

In most cases, having one blue fingernail is not an emergency, but it still merits a trip to the doctor for evaluation. It is important to rule out any serious underlying conditions.

You should make an appointment with your primary care physician or a dermatologist when:

– The discoloration appeared without any obvious injury to the nail

– The blue color does not go away after 4-6 weeks

– The nail has changed in thickness or texture

– Other nails begin to change colors or show odd markings

– The fingertip under and around the nail is also blue

– You have any additional symptoms like pain, numbness, or swelling

Do not wait and assume it is nothing – early examination and testing can pick up issues like melanoma when it is still treatable.

Questions the Doctor May Ask

When you visit the doctor about a blue fingernail, some questions they may ask include:

– When did you first notice the change in color?

– Have you suffered any recent injury to the finger or nail?

– Do any other nails have discoloration or changes in texture?

– Do you have any pain, numbness, or discomfort in the finger?

– Do you have any other accompanying symptoms like nail thickening or detachment from the nail bed?

– Could the blue color be due to exposure to cold temperatures or emotional stress?

– Do you have any existing respiratory conditions that could be causing low oxygen levels?

– Do you have a family history of melanoma or other skin cancers?

Physical Exam and Tests

After discussing your health history, the doctor will likely perform a physical exam of your hands and fingers. They may gently press on the nail and surrounding skin to check for pain or swelling.

Your doctor may be able to diagnose benign bruising based on appearance alone. But they will likely want to do some tests or refer you to a dermatologist depending on the examination findings.

Some examples of possible tests include:

– Blood work to check for infections or systemic issues

– Testing oxygen saturation levels

– X-ray to look for broken bones or other injury

– Biopsy of the nail to check for fungal infection or melanoma cells

– Removal of part of the nail to examine the nail bed

Treatment Options

The appropriate treatment will depend on the underlying cause of the blue fingernail:


No specific treatment is needed for bruising. It will resolve on its own over several weeks as the blood reabsorbs. Use over-the-counter pain medication as needed.

Fungal Infection

A topical antifungal cream may be prescribed for mild cases limited to the fingernail. Oral antifungal tablets are used for more severe or persistent fungal nail infections. Removing part or all of the infected nail may also be done.


Treatment involves surgically removing the melanoma cells and a margin of surrounding healthy skin to help prevent recurrence. Some lymph nodes near the cancer site may also be biopsied or removed.

Raynaud’s Phenomenon

Lifestyle changes like avoiding cold exposure, quitting smoking, and managing stress can help reduce Raynaud’s attacks. Medications to open blood vessels or thin the blood may be prescribed in more problematic cases.

Low Oxygen

Addressing any underlying lung or heart conditions can help improve oxygenation to the tissues. Supplemental oxygen may be given. Cyanosis caused by living at high altitudes usually does not require treatment.

Prevention Tips

While a single blue fingernail is often out of your control, you can take some precautions to keep nails healthy and lower risks:

– Wear gloves when handling chemicals or dirty/irritating substances

– Moisturize nails and cuticles daily

– Trim nails straight across to avoid ingrown edges

– Treat minor nail injuries promptly

– Avoid picking at nails or cuticles

– Wear shoes that fit well to prevent toe impact and injury

– Examine nails regularly for any changes in color or texture

– See a doctor promptly if you notice any unusual spots or nail discoloration

– Apply sunscreen on hands or wear gloves to protect from UV damage and skin cancer

When to Seek Emergency Care

Most cases of a single blue fingernail are not emergencies. However, seek immediate medical care if:

– The fingernail is injured and torn off or partly ripped off

– There is significant trauma to the finger resulting in uncontrollable bleeding

– The finger appears deformed or angulated suggesting a break or dislocation

– The entire finger is blue or has numbness, tingling, severe coldness

– You have symptoms of a heart attack including chest pain, shortness of breath

– You have signs of a stroke such as face drooping, arm weakness, speech issues

Outlook and Prognosis

For the vast majority of causes, having one blue fingernail is not serious, and the long-term outlook is good. Discoloration from bruising or Raynaud’s will resolve in a few weeks to months. Fungal infections can be cured over 6-12 months with antifungal treatments.

The biggest concern is if the blue nail is a sign of subungual melanoma. When diagnosed extremely early, the 5-year survival rate is around 90%. However, the prognosis declines rapidly as the cancer advances beyond very initial stages.

Catching any unusual nail changes right away offers the best chance for full recovery and prevents complications. Monitoring your nails and acting quickly when you spot abnormalities is extremely important.

When to Follow Up

You should schedule a follow up appointment with your doctor:

– If the blue color remains after 2-4 weeks of bruising or cold exposure

– To monitor improvements from antifungal medication

– To ensure melanoma has not recurred after surgical removal

– If Raynaud’s symptoms fail to improve with initial treatment

– To check oxygen levels if cyanosis was caused by a respiratory or cardiac condition

– Anytime new symptoms develop or existing symptoms get worse

Careful monitoring and follow up is crucial for diagnosing the cause and checking treatment effectiveness. Don’t hesitate to call your doctor sooner if you have any worries about progression.


While a single blue fingernail may seem like a trivial issue, it should not be ignored. The most likely causes are bruising, fungal infection, melanoma, Raynaud’s syndrome or low oxygen levels. Seeing a doctor right away for proper evaluation is important to determine the underlying condition.

With treatment guided by the diagnosis, most causes beyond trauma can be resolved over weeks to months. Catching a rare case of subungual melanoma early is critical. Consistent follow up and monitoring allows problems to be caught before they advance and leads to the best outcomes. Paying attention to changes in your nails and getting examined at the first sign of trouble is always recommended.

Leave a Comment