I'm having trouble sleeping. Could this be caused by my supplements: a multivitamin, fish oil, magnesium, calcium, vitamins D and K, and protein. I'm also on a low-dose blood pressure medication.

Answer:

Among these supplements, vitamin D seems the most likely cause. Multivitamins, fish oil, magnesium, calcium, vitamin K and protein supplements are not generally known to cause insomnia. High doses of vitamin D, as well as high blood levels of vitamin D have been associated a deterioration in sleep quality — and you seem to be supplementing with both vitamin D and a multivitamin that likely provides more vitamin D. High amounts of vitamin D may interfere with the body's production of melatonin. 

For more about this, see the Concerns and Cautions section of the Vitamin D Supplements Review. Also see the section How Much Is Too Much? regarding getting the right amount of vitamin D. 

Be aware that beta blocker medications, such as atenolol (Tenormin) and metoprolol (Lopressor, Toprol XL) that help lower blood pressure may also lower your body's nighttime production of melatonin and interfere with sleep. A small study suggests that melatonin supplementation may improve sleep in people taking these medications. However, be aware that melatonin may increase blood pressure in people taking another type of blood pressure lowering medication. See the Concerns and Cautions section of the Melatonin Supplements Review for more about this.