The information presented here does not constitute medical advice, and is not intended to be a substitute for a consultation with your medical doctor.

The frequency with which doctors prescribe blood testing varies greatly from country to country, and tends to reflect public health priorities rather than your individual needs and opportunities.

So how often should you really get a blood test?

Routine blood work

Your doctor will typically recommend that you get routine blood tests, including a complete blood count (CBC) and a complete metabolic panel, at least once a year, around the same time as your physical checkup.

It is highly recommended that you do the routine blood test every year, independent of your age, given the low cost and potential to identify serious diseases and nutritional deficiencies early on, before you become symptomatic.

Regular blood testing

The yearly blood work is the bare minimum, but there are reasons to get your blood tested more frequently:

• You are experiencing unusual, persistent symptoms. These can include fatigue, anxiety, skin or nail abnormalities, hair loss and weight gain.
• You are making changes to your diet or lifestyle. For example, if you decide to become vegetarian, take new supplements, or follow an intense exercise regimen.
• You want to optimize your health. Knowing levels of various blood components can allow you to tweak your diet or fitness plan to minimize unhealthy habits.
• You want to reduce your risk of disease or complications. Regular blood tests can catch the warning signs of almost any disease early.
• You already suffer from a chronic/degenerative disease. Doctors use test results to evaluate the treatment of diabetes, hypertension, dyslipidemia and other diseases.

Most healthy individuals can benefit from getting their blood tested between two and four times a year, particularly if they make major changes to their lifestyle or diet, or want to reduce their risk of developing new diseases.

Your blood cells are replaced every few months, so excluding a few select biomarkers, you won't see your lab results change overnight.

Following a lifestyle change, new supplements or medications, you should see changes in your blood composition within a few weeks or months.

For example, even though changes in fasting glucose levels can be seen after a short period of time, other biomarkers for diabetes, such as HbA1c, won't be affected until after a couple of months.

Is it dangerous to get blood draws too frequently?

The volume of blood needed to conduct a blood test is negligible to your system, and it is perfectly safe to get a blood draw multiple times a year.

If you do a blood test every day for a prolonged period of time, such as when you are in a hospital, you may develop a condition in which you don't have enough red blood cells to carry oxygen through your body.

The side-effects of having a blood draw once a month, however, tend to be limited to a mild pain from the needle and the discomfort of having the blood drawn, both of which you will get used to over time.