Fasting is not required for a PTH (parathyroid hormone) blood test. You can eat and drink normally before the test. However, there are some important timing considerations: PTH levels naturally fluctuate throughout the day, with higher levels typically in the early morning and lower levels in the afternoon. For this reason, your doctor may request that you have the test done at a specific time, usually in the morning, to ensure consistent and comparable results. Some labs prefer morning samples between 8-10 AM. If you're taking any medications, especially calcium supplements or vitamin D supplements, ask your doctor whether you should temporarily stop them before the test, as these can affect PTH levels. You should also let your healthcare provider know about any recent illnesses or medications you're taking, since various conditions and drugs can influence PTH results. While fasting itself isn't necessary, arriving well-hydrated and in a calm state is beneficial for any blood draw, as stress and dehydration can affect blood chemistry. If your doctor hasn't given you specific instructions about preparation, you can safely assume normal eating and drinking are fine—just aim for the recommended time window if one was provided.