For many people, a haemoglobin level of 17.3 g/dL is somewhat higher than usual. This can be caused by dehydration, smoking, living at a high altitude, intense activity, insufficient sleep, or occasionally illnesses that affect the blood, heart, or lungs. If dehydration or smoking is the cause, it may be helpful to drink enough water, abstain from smoking, limit alcohol, and lead a healthy lifestyle. However, you should see a doctor for additional testing to determine the precise cause if the level remains elevated on subsequent testing or if you experience symptoms like headache, dizziness, redness, breathing difficulties, or elevated blood pressure.