Can a negative blood test be wrong after three missed periods because had 3 since coming off the pill but and hpt tests have been negative?

It is possible for a blood test to be wrong after three missed periods, even if home pregnancy tests (hpt) have been negative. Here are a few reasons why:

1. Early Pregnancy: If you are very early in your pregnancy, the levels of human chorionic gonadotropin (hCG), the hormone detected in pregnancy tests, may still be low to be detected in a blood test. In some cases, it may take several days or even weeks for hCG levels to rise to detectable levels.

2. Irregular Periods: If you have irregular menstrual cycles, it can be challenging to determine the exact timing of ovulation and conception. This can lead to confusion about the number of missed periods and potentially affect the accuracy of pregnancy test results.

3. Ectopic Pregnancy: In rare cases, a negative blood test could occur if the pregnancy implant outside the uterus, known as an ectopic pregnancy. Ectopic pregnancies can cause missed periods but may not be detected in standard blood tests.

4. Medical Conditions: Certain medical conditions, such as hypothyroidism or pituitary gland disorders, can affect the production or detection of hCG. In these cases, the results of pregnancy tests, including blood tests, may be inaccurate.

5. Test Error: While blood tests are generally reliable, there is a slight possibility of lab error or mishandling of samples, leading to incorrect results.

Given the conflicting results between your missed periods and negative hpt and negative hpt tests, it's important to follow up with your healthcare provider. They may recommend repeating the blood test or perform additional tests, such as an ultrasound, to determine whether you are pregnant and address any underlying causes of your missed periods.