Hemoglobin 18.7 g/dL: Is That High?

Is Hemoglobin 18.7 g/dL Low, Normal, or High?

Hemoglobin 18.7 g/dL is above the normal range and is considered elevated. The standard hemoglobin range is 12.5 to 17.5 g/dL, placing 18.5 above the upper limit. Hemoglobin is the oxygen-carrying protein in your red blood cells, and having too much of it can be a concern just as having too little can. An elevated hemoglobin level means your blood contains more red blood cells or more concentrated hemoglobin than typical, which can make your blood thicker and harder to circulate. This condition is generally referred to as polycythemia. While there are benign explanations for mildly elevated hemoglobin, this result warrants investigation by your doctor to determine the cause.

A hemoglobin level measuring 18.7 g/dL indicates a clinically high reading, exceeding the upper limit of the normal range by a notable margin. This elevation often signals that the body might be producing too many red blood cells or that the blood is unusually concentrated. Common reasons for this specific reading include dehydration, where a lack of fluids artificially increases the concentration of blood components, or the body compensating for chronic low oxygen levels, as seen in conditions like sleep apnea, chronic lung disease, or even prolonged residence at high altitudes. While less common at this precise level, a persistent elevation could also hint at primary polycythemia, a bone marrow disorder that requires careful investigation. Your healthcare provider will likely recommend a retest to confirm the 18.7 g/dL value, often alongside a comprehensive metabolic panel to assess hydration and a detailed complete blood count. You might also be asked about lifestyle factors, medication use, and recent travel. Patients should know that even a moderately elevated hemoglobin, if persistent, can increase blood viscosity, potentially raising the risk of blood clots or putting extra strain on the heart over time, making it vital to identify and address the underlying cause promptly for long-term health.

Hidden Risk of Hemoglobin 18.7 g/dL

A hemoglobin of 18.7 g/dL may not cause noticeable symptoms right away, but elevated hemoglobin carries risks that are important to understand. When your blood is thicker than normal, it moves more slowly through your vessels, and this can create problems in your circulatory system. The American Society of Hematology notes that persistently elevated hemoglobin increases the risk of several serious complications.

A hemoglobin level of 18.7 g/dL, significantly above the typical female range, elevates the risk of blood clots due to increased blood viscosity. This thicker blood flows less smoothly, making it more prone to forming dangerous clots in veins or arteries, which can lead to serious events like deep vein thrombosis, pulmonary embolism, stroke, or heart attack. The increased red blood cell mass also puts extra strain on the heart, potentially exacerbating pre-existing cardiovascular conditions or contributing to the development of hypertension over time. This elevated state suggests a potential underlying condition that warrants thorough investigation to prevent these potentially life-threatening complications.

Risks associated with hemoglobin at 18.7 g/dL include:

• Blood clots, including deep vein thrombosis (DVT) in the legs and pulmonary embolism in the lungs
• Increased risk of stroke due to thickened blood moving through small vessels in the brain
• Heart attack risk rises because the heart has to work harder to pump thicker blood
• Headaches, dizziness, and blurred vision caused by sluggish blood flow to the brain
• High blood pressure, as thicker blood creates more resistance in the arteries
• Itchy skin, particularly after a warm shower or bath, which is a classic symptom of polycythemia vera
• Gout caused by elevated uric acid levels, which can occur when excess red blood cells break down

What Does a Hemoglobin Level of 18.7 g/dL Mean?

Hemoglobin is the oxygen-carrying protein inside your red blood cells. Each hemoglobin molecule picks up oxygen in your lungs and delivers it to cells throughout your body. When hemoglobin is measured at 18.7 g/dL, it means there is more of this protein in your blood than the body typically needs. While it might seem like more oxygen delivery would be a good thing, too much hemoglobin actually creates problems. Thicker blood does not flow as smoothly, and the increased viscosity can slow circulation, raise blood pressure, and increase the risk of clotting. The National Institutes of Health identifies several possible reasons for elevated hemoglobin. The most common is dehydration, which temporarily concentrates your blood and can make hemoglobin appear higher than it truly is. Living at high altitude is another common cause, as your body produces more red blood cells to compensate for lower oxygen levels in the air. Smoking can also raise hemoglobin because carbon monoxide from cigarettes reduces the oxygen-carrying efficiency of each hemoglobin molecule, prompting your body to make more. Chronic lung diseases like COPD can have a similar effect. In some cases, elevated hemoglobin points to polycythemia vera, a bone marrow disorder where the body produces too many red blood cells. Less common causes include kidney tumors, testosterone use, and certain performance-enhancing drugs. Your doctor can use additional tests to determine which category your elevation falls into.

For a hemoglobin reading of 18.7 g/dL, the most probable causes often involve dehydration, which concentrates the blood and temporarily elevates this value, or the use of erythropoiesis-stimulating agents (ESAs) like epoetin alfa, often prescribed for anemia related to kidney disease or chemotherapy. Another significant consideration is polycythemia vera, a rare blood disorder where the bone marrow produces too many red blood cells, though other polycythemic conditions, including those related to high altitude living or smoking, are also plausible. Less likely, but still possible, are certain tumors that secrete erythropoietin.

Lifestyle Changes for Hemoglobin 18.7 g/dL

If your hemoglobin is elevated at 18.7 g/dL, certain lifestyle adjustments can help manage your levels while your doctor works to identify the cause. Hydration is the single most important factor. Dehydration concentrates your blood and raises hemoglobin readings, so drinking plenty of water throughout the day, especially in warm weather or during exercise, is essential. Aim for at least eight glasses of water daily, and more if you are physically active or live in a hot climate. If you smoke, quitting is strongly recommended. Smoking is one of the most common causes of elevated hemoglobin, and the Mayo Clinic lists smoking cessation as a key step in managing high hemoglobin. Your body produces extra red blood cells to compensate for the carbon monoxide in cigarette smoke, and stopping allows hemoglobin to normalize over time. Regular moderate exercise helps maintain cardiovascular fitness, but avoid extreme endurance training at high altitudes, as this can further stimulate red blood cell production. If you live at high elevation, be aware that some degree of elevated hemoglobin is a natural adaptation, but discuss with your doctor what level is safe for you. Avoid very hot baths and saunas if you experience itchy skin, as heat can worsen this symptom. Be mindful of any supplements or substances that might increase red blood cell production, including anabolic steroids or testosterone, and discuss these with your doctor.

With a hemoglobin reading of 18.7 g/dL, immediate action is crucial. Schedule a follow-up test within 48-72 hours, ensuring adequate hydration in the interim by drinking plenty of water, and abstain from alcohol. If you are taking any medications, especially injections like ESAs, confirm the dosage with your prescribing physician. You should also consult with your primary care physician to discuss potential underlying causes and may need a referral to a hematologist for further investigation, including blood counts and genetic testing if polycythemia vera is suspected. Tracking symptoms like headache, dizziness, or shortness of breath is also advised.

Written by

Ernestas K.

Clinical research writer specializing in human health, biology, and preventive medicine.

Reviewed against ASH, NIH, Mayo Clinic, CDC guidelines · Last reviewed March 20, 2026