Supplements for energy and tiredness
Iron, B12, vitamin D, B complex and magnesium: which one depends on a blood test. What each contributes to, and what to skip.
How to choose a supplement for tiredness
More energy through the day starts with the nutrient you are actually short of. Iron, B12, vitamin D and the B vitamins each lift energy when they are low, and a simple blood test tells you which one applies to you. The products here are the forms that absorb well and are gentle to take.
Why these
Iron & Vitamin C: Restores energy where low iron is the cause, without the constipation of standard iron. Vitamin C in the same capsule increases absorption.
Methylcobalamin Vitamin B12 Capsules: Lifts tiredness when B12 is low, in the active form the body uses straight away. 1000 mcg per capsule.
Vitamin D3 & K2: Supports energy, mood and immunity through the winter months, when UK sun is too weak to make any. 2500 IU with K2.
B Complex Liquid: All eight B vitamins for steady energy and stress resilience, in the methylated forms, absorbed fast as drops.
Magnesium Malate: The daytime magnesium: supports energy production and eases tired muscles without making you sleepy.
Read the evidence
Free blood test result interpreter · How long does iron take to work? · How long does B12 take to work?
If you take prescribed medicines, are pregnant or breastfeeding, or have a diagnosed condition, talk to your GP or pharmacist first. Not sure which fits? Ask Nutri365, the Nutri Tailor AI health expert, which checks for interactions and contraindications.
Common questions
Which supplement should I take for tiredness?
The one your blood test points at. Low ferritin points at iron, low B12 at B12, a winter result at vitamin D. Without a test, the honest answer is that nobody knows, which is why this page starts with the interpreter.
How long does iron take to work?
Two to four weeks to lift haemoglobin and three to six months of continued use to refill ferritin stores, which is why UK guidance advises carrying on after you feel better.
Should I take vitamin D in winter?
UK guidance is that everyone considers a daily supplement from October to March, because the sun is too weak in the UK to make vitamin D in those months.
Written by Nutri Tailor from the Health Reference Library. Last checked 6 September 2026. General information, not personal advice.