lab-guides

The B12 level test measures B12 in the blood; an MMA test may be added, since a high MMA may be due to B12 deficiency. Some medicines affect the result.

TSH is the pituitary's signal to the thyroid; Free T4 and T3 measure thyroid hormone. Read together, they help show whether a problem starts in the thyroid or the pituitary.

HbA1c gives an average of blood glucose over the past two to three months. Per the CDC: below 5.7% normal, 5.7–6.4% prediabetes, 6.5% or above diabetes.

The 25-hydroxy vitamin D test measures how much vitamin D is in your body. How to read your result against the published levels, and what moves it.

RBC folate is a longer-term measure of folate intake than serum folate. Folate is needed to make DNA, for methylation and to keep homocysteine low.

Fibrinogen is a protein made in the liver that helps blood clot. How to read your fibrinogen result against the lab's range.

Ferritin is a protein that stores iron, and the ferritin blood test indirectly measures how much iron your body has stored. How to read a low or high result.

A fasting insulin test measures insulin after an 8–12 hour fast. Read with glucose and other tests, it helps a clinician assess insulin resistance.

Blood glucose measured after a fast of at least 8 hours, read against the published normal (70–99 mg/dL), prediabetes (100–125) and diabetes (126+) cut-offs.

Estradiol is the main estrogen of the reproductive years. Its level changes across the menstrual cycle, so read a result with cycle day or menopausal status.

DHEA-S is an adrenal hormone that peaks around puberty and declines with age, so the result is read against age- and sex-specific ranges.

Serum creatinine and the calculated eGFR estimate the kidney filtration rate. Creatinine varies with muscle mass, so read the result in that context.